The Pipe
A pipe, obviously, is used to smoke marijuana. Marijuana is placed in the bowl and burned, while smoke is inhaled through the shaft and into the mouthpiece. The elbow piece simply holds together the mouthpiece and shaft.
Some pipes have a resonator, which would most likely be somewhere within the shaft. Pipes that have a shorter shaft will have a harsher toke. If the shaft is long, the smoke will cool as it travels to your mouth, and you will be able to take more smoke comfortably.
Pipes are usually used by people who are in a hurry, don't have enough money for a bong, can't roll joints well, and/or need a portable method of smoking up.
Making Your Own Pipe
A pipe can be purchased for a price as low as $5 at any head shop and many corner stores. However, if you feel the need to make your own, or are caught without your pipe, there are many ways to make your own pipe. Here are a couple of the ones I prefer to use:
The Pop Can
Drink or dump out as much pop as possible, it's not cool having pop leak into your mouth in the middle of a toke. Rinse it out if you can, so you can more enjoy the flavour of your weed. Flatten the top down so that you have a relatively safe surface on which to place your weed. Using a safety pin (or something of the sort) poke small holes (if you poke holes too big, your weed will fall through) around the center of the flattened top of your can. This is where your weed will be held. Torch the weed above the holes and inhale through the drinking hole of the pop can. This method works quite well, but it's not a good pipe to use constantly, some say aluminum is rough on your lungs.
The Plastic Bottle
This method requires tinfoil, as well as a water/pop bottle. Obviously, your first step is emptying out the bottle of all contents. Burn or cut a hole large enough for a bowl of weed towards the end of the bottle. Now, using the tinfoil, make a bowl and fit it into the hole in your bottle. Poke holes (once again, not too big) through the bottom of your tinfoil bowl and place your weed into the bowl. Torch the weed and inhale through the top of the bottle. This method is known to give great cream.
Highlighter
For this, all you really need is a highlighter. Open it up and empty out the ink cartridge and such from the inside of your highlighter. Burn a hole in the side of your highlighter towards the end, just big enough so that the cap for your highlighter fits in snugly. Cut a hole in the bottom of your cap, and either use tinfoil as a filter or put in a screen so your weed doesn't fall into the highlighter. You've now got your basic pipe. Inhale through the end which was previously covered by the cap. I personally don't like this method... for some reason inhaling through a pipe that previously held toxic chemicals is slightly disheartening.
Apple Pipe
This one takes a bit of work, and tools, but it's fun to use (and quite funny to look at while you're stoned). You start off with a knife and an apple. Your first step is to take the core out of the apple, but don't pierce the bottom of the apple. Then, take a pen and empty it out so you just have the tube. Stick the pen into the side of the apple so it goes into the hollow chamber of your apple. Remove the pen and take the apple bits out of the tube. Put the tube back into the apple. Now, make a bowl out of tinfoil and place your bowl ontop of the apple, covering the hole. This, obviously, can't usually be used more than once, as the apple will start to rot. This one is great entertainment to make at parties, and gives a sweet taste to your stash.