FORM Present Continuous
[AM / IS / ARE] + [VERB+ing]
EXAMPLES:
I am watching TV.
He is quickly learning the language.
NOTE: When you are using a verb tense with more than one part such as
Present Continuous (is learning), adverbs often come between the first part and
the second part (is quickly learning).
USE 1 Now 
Use the Present Continuous with
Continuous Verbs to express the idea that something is happening now,
at this very moment. It can also be used to show that something is not happening
now.
EXAMPLES:
You are learning English now.
You are not swimming now.
I am sitting.
I am not standing.
They are reading their books.
They are not watching television.
What are you doing?
Why aren't you doing your homework?
USE 2 Longer Actions in Progress Now 
In English, now can mean "this second," "today," "this month," "this
year," "this century" and so on. Sometimes we use the Present Continuous to say
that we are in the process of doing a longer action which is in progress;
however, we might not be doing it at this exact second.
EXAMPLES: (All of these sentences can be
said while eating dinner in a restaurant.)
I am studying to become a doctor.
I am not studying to become a dentist.
I am reading the book Tom Sawyer.
I am not reading any books right now.
Are you working on any special projects at work?
Aren't you teaching at the University now?
USE 3 Near Future 
Sometimes, speakers use the Present Continuous to indicate that something will
or will not happen in the near future.
EXAMPLES:
I am meeting some friends after work.
I am not going to the party tonight.
Is he visiting his parents next weekend.
Isn't he coming with us tonight.
USE 4 Repetition and Irritation with
"Always" 
The Present Continuous with words such as "always" or "constantly" expresses the
idea that something irritating or shocking often happens. Notice that the
meaning is like
Simple Present but with negative emotion.
Remember to put the words "always" or "constantly" between "be" and "verb+ing."
EXAMPLES:
She is always coming to class late.
He is constantly talking. I wish he would shut up.
I don't like them because they are always complaining.
IMPORTANT Non-Continuous Verbs/ Mixed
Verbs
It is important to remember that
Non-Continuous Verbs cannot be used in any "continuous" tenses. Also,
certain "non-continuous" meanings for
Mixed Verbs cannot be used in "continuous" tenses. To express the
idea of "happening now", you must use
Simple Present USE 3.
EXAMPLES:
She is loving chocolate.
Not Correct
She loves chocolate. Correct
ACTIVE / PASSIVE Present Continuous
EXAMPLES:
Right now, Tom is writing the letter.
ACTIVE
Right now, the letter is being written by Tom.
PASSIVE