Dog Agility is the "sport" where dog and handler team work together to complete a course of Jumps, Tunnels, Weave Poles, and Heavier Equipment.
There are many different venues and I run in them three of them.  This will make it confusing, but I think I can pull off an explanation.

Also, I have been away from the Agility Sport for a few years.  Just before Crumpet was retired, NADAC and AKC were both implementing new courses and rules.  There are many more "Games Classes" offered then what I have here, but for starters in explanation, I have what I have below.

 The Venues:
AKC (American Kennel Club)
USDAA (United States Dog Agility Association)
NADAC (North American Dog Agility Council)

The Course Difference:
AKC is known for its tight courses.  One of the complaints from four years ago was there was no way for the dog to be in a safe position for many of the technical obstacles.

USDAA is known for its flowing course and Handler restricting technicalities.

NADAC is known for its wide space between obstacles and fast pace.

Depending on which one you chose, do not be fooled by any of the Course Designs.  Judges have developed their running lines for particular reasons and you as the Handler are guaranteed to be challenged.

Levels Offered:
AKC - Novice A&B, Open, Excellent A, Excellent B. 
Novice A is for people who have never handled a dog to an AKC Novice title.
Novice B is for those who have. 
Excellent A is for the teams going for the Excellent title.
Excellent B is for those that are going for the Masters or Agility Championship.

USDAA - Starters/Novice, Advanced, Masters. 
Starters is for anyone who has not gotten an "AD" on a dog.
Novice is for those that have.

NADAC - Novice A&B, Open, Elite
Novice A is for anyone who has never gotten a first level title in any venue.
Novice B is for those who have.

The Equipment on the Course:
Jumps - Wooden or PVC posts with displaceable bars (for safety).  Jumps come in the single, double, and triple variety.  Bars must stay up.

Tire Jump - A jump that is in the shape of a tire.  The tire is attached to a PVC frame.  Dogs must jump through the tire, avoiding the easy route of through the sides.

Panel Jump - A jump that is solid looking.  Usually it is made of wood and is the same as the ones used in obedience.  All wooden panels are displaceable.

Broad Jump - There are wooden boards set up on the ground.  The dog must jump the distance the long way instead of up and over.

Tunnels - Just as they are.  They can be straight or bent.  They can also appear under the Frame and DogWalk for trap or discrimination purposes.

Chute - A barrel on its side with a 10 - 20 foot flat nylon cloth attached.  The dog must enter one end and push through the "chute" part.

Table - A 36inch square table.  Dog must jump on and do prescribed command (sit or down) for the count of five.  Once completed, the Team continues on.

Teeter Totter - Just like the ones you find in the playground.  Dog must go up, control the descent, touch the "yellow area" at the bottom, and then go on.

Dog Walk - (Also known as "DW")  A series of three boards.  Each board is 8 feet long.  The two end ones serve as ramps going up and down, the one in the middle is flat.  The height of the middle board can be 3 or 4 feet.  The dog must touch the "yellow area" at the descending bottom.

Frame - Two 8 foot panels that come together at the top to form an "A".  Dogs must go up one end, touch the "yellow area" at the bottom, and then continue on.  The difference in height at the top can be 5'6" to 6'3".  This may sound small, but the angle of the boards to the ground is very different.

Weave Poles - These are a set of 12 poles, set 20" apart.  The dog must enter from the same "entrance" and "weave" in and out until complete.  (This is one of the most difficult and time consuming exercises to teach, but once the dogs "get it" the results can be absolutely amazing to watch.)

The Rules:
Non - Qualifying (NQ)
     Dropped bar on jump.
     Jumped "yellow area" on the Frame, DW & Teeter.
     Exceeding Course time (NADAC & USDAA).
     Exceeding refusal limits (AKC).

 Qualifying (Q)
     Do nothing to screw up.
     : )

Courses Offered:

AKC � Standard, Jumpers with Weaves

USDAA � Standard, Jumpers, Gamblers, Snooker, Relay

NADAC � Standard, Jumpers, Gamblers

  Standard (AKC, USDAA, NADAC):
This is a course that is designed from the Start Line to the Finish Line by the judge.  You must take each obstacle in the order that it is numbered.
This course will have all of the equipment, with the exception of NADAC.  (They do not have the Table.)
Depending on which level you are running determines how difficult the course is. 

  Jumpers (USDAA, NADAC) / Jumpers With Weaves (AKC):
The course has nothing but jumps, tunnels, chute, tire, and in the case of AKC, weaves.
It is meant for speed and accuracy.  Again, this course is totally determined by the judge from start to finish.

  Gamblers (USDAA, NADAC):
The course has two segments.  The first half is Handler determined and the second half is judge determined.  The idea is for the team to accumulate a certain number of points (depending on the level) before the whistle blows.
When the whistle does blow, the team moves to the "Gamble" area that is set up by the judge.  The catch is that these obstacles are done at a distance.  The dog has to be sent out or called in.  The team has about 15 seconds to complete this last part.  Once the second whistle is blown, the team either hauls butt to the Table or to the Finish Line to stop time.
The dog must do the Gamble in order to Qualify. 

  Snooker (USDAA):
This course also has two segments.  The opening is left to the Team to design.  The dog must do three "red jumps" (they are not really red, just called that).  The ending or Closing Sequence is determined by the judge.
The Opening will look like.....Obstacle, Red Jump, Obstacle, Red Jump, Obstacle, Red Jump, Obstacle, and then on to the Closing Sequence.

The whole idea is to get as many points as possible before the whistle is blown.  Depending on the level you are running depends on how many points you need.  Once you hear the whistle, you have to haul butt to the Finish Line to end time.
  There are a ton of rules that are still boggling to me.  I am sorry if I am vague here, but I am vague on course too.

   Pairs Relay (USDAA):
This is a full course that is split halfway.  One Team completes the first half, the second Team finishes the other half.  Each Handler has to carry a Baton in hand and it is passed on within a "Judge's Box" - designated area.

Sometimes, Teams are allowed to pick half to perform, but there are Judges that will make that decision.  The pairs qualify together with disqualification for the dogs to going off course or the number of faults collected exceed the time limit.  Dropped bars and jumped contacts (yellow areas) are considered "faults" and are awarded a five-point penalty resulting in time being added to the clock.

Ribbons:

  Once the course is complete, you tend to know if you have Qualified or not.  Depending on the venue is whether or not you walk away with Mother Club appreciation or not.

 AKC - Q runs will only be awarded a placement ribbon (if acquired).

USDDA & NADAC - Both of these organizations will award placement ribbons to all teams as long as they are in the running.  (If only two dogs Q, the chance of getting a third or fourth place ribbon is there.)

Titles:
Each different venue has different requirements, but each win is considered a "leg"

AKC Novice A&B -   NA (Novice Agility) 3 legs   NAJ (Novice Agility Jumpers) 3 legs Open   OA (Open Agility) 3 legs   OAJ (Open Agility Jumpers) 3 legs Excellent A   AX (Excellent Agility) 3 legs   AXJ (Excellent Agility Jumpers) 3 legs Excellent B   MX (Master Agility) 10 legs   MXJ (Master Agility Jumpers) 10 legs Master Agility Champion   MACH  20 "Double Qs"   & 750 points

NADAC Novice A&B   NAC (Novice Agility Certificate) 30 points   NJC (Novice Jumpers Certificate) 20 points   NGC (Novice Gamblers Certificate) 20 points Open   OAC (Open Agility Certificate) 30 points   OJC (Open Jumpers Certificate) 20 points   OGC (Open Gamblers Certificate) 20 points Elite   EAC (Elite Agility Certificate) 30 points   EJC (Elite Jumpers Certificate) 20 points   EGC (Elite Gamblers Certificate) 20 points NADAC Agility Champion   NATCH   (When I figure this out, I will post it.)

USDAA Starters/Novice   AD (Agility Dog) 3 legs Advanced   AAD (Advance Agility Dog) 3 legs           (Advanced Jumpers) 2 legs for move up           (Advanced Gamblers) 2 legs for move up           (Advanced Snookers) 2 legs for move up           (Advanced Pairs/Relay) 2 legs for move up Masters   MAD (Master Agility Dog) 5 legs   MJ    (Master Jumper) 5 legs   MG    (Master Gambler) 5 legs   MS    (Master Snooker) 5 legs   MR    (Master Relay) 5 legs Agility Dog Champion   ADCH   Collect all 5 Master Titles with 2 Super Qs per title.

The Beanhead Emails:
There are some things that I refer to on a normal basis that has its origins in past Beanhead emails.  Some of the recipients had a hard time keeping track of the terminology and I found myself re-explaining within each email.  At that time, I wrote up these explanations and referred all to a link to a web page.

Obviously, Crumpet and Sprout have been long retired, with Fred and Harry being handled by other people.  The below no longer applies to 'my real time', but may help in relaying what was going on at the time the Beanhead Emails were being written.

"Dog Walk" - I often refer to the shortened name of DW.  It makes it so much easier to type this out.

"Jumping the contact area" - Crumpie and Harry are famous for jumping this area on the DW and are always NQed because of it.

"Knocking bars" - Oh boy does this happen more then I would like it to.  Fred will take almost everyone out, Crumpie one or two, and Harry will take one out if I am not careful.  This also NQs us.

"The Tip and The Table" - These are two issues that Harry Faces. In other words, he has a hard time performing these, especially if it is a "down" on the Table.

"The Table" - Crumpie has decided that the Table is something that we need to struggle with.  He will often jump off of it while barking.

"Vacuum Sucked Tunnels or Yummy Tunnels" - Corgis have this thing for Tunnels.  If a tunnel is placed on the course, but it is NOT part of the course (numeric order), the Tunnel becomes Yummy.  If it is part of the course, it is a normal tunnel. In other words, a Yummy Tunnel is a trap.

"The Clothes Line" - This is a simple, well, clothes line that we string up across the front of our tent to hang our ribbons on.  The better our weekend, the more it is filled.

"First of the Losers" - A comment made by Beth M at one trial and it has stuck in my head.  This is used when we are running in NADAC and USDAA.  Placement ribbons can be handed out to the top contenders.  If you happen to get the first Non-Qualifying ribbon, you are basically the first place loser...even though you might have been awarded a third or fourth place.