This tense is called the Continuous Present Perfect. There is usually a connection with the present or now. 

a) An action that has just stopped or recently stopped
To talk about an action that started in the past and stopped recently. There is usually a result now.

I'm tired (now) because I've been running.

Why is the grass wet (now)? Has it been raining?

You don't understand (now) because you haven't been listening.

b) An action continuing up to now
To talk about an action that started in the past and is continuing now. This is often used with 'for' or 'since'.

I have been reading for 2 hours.
(I am still reading now.)

We've been studying since 9 o'clock.
We're still studying now.

How long have you been learning English?
(You are still learning now.)

We have not been smoking.
(And we are not smoking now.)

We use 'for' to talk about a period (5 minutes, 2 weeks, 6 years). We use 'since' to talk about a point (9 o'clock, 1st January, Monday).

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