The present continuous tense is used to show we are in the middle of an activity that is still in progress. The activity started in the past and will go on in the future.
Examples: I am reading / I'm writing. So when we use the present continuous tense we are talking about something that is still not yet finished or complete at the time of speaking.
The present continuous tense of any verb is formed with the simple present tense of the verb to be (=am, is, are) and the present participle of the main verb (verb + ing)
Example: I am eating a pie for lunch.
Example: Mike is walking out after a row with his girlfriend.
Example: Police are looking through a pile of papers and still haven't found what they want.