Hi aaisha86,
the Present Perfect Continuous
is used:
1) for an action that started in the past and is still going on in the Present:
He�s been watching TV all
day.
2) for actions repeated over a period of time:
Debbie has been playing
tennis since she was eight.
3) for actions that have finished
right now, stressing the duration:
I�ve been waiting for half an hour!
The activity is of interest, whereas in
Present Perfect Simple the result is the important thing. Often it tells you
how long something has been going on, whereas the Present Perfect Simple may
give information about how often/how many times something has happened.
example:
Mary has been
writing letters all day. - how long? -> Present Perfect Continuous
Mary has written four letters today. - how many? -> Present Perfect Simple
Hope that helps, best wishes from Austria,
Elisabeth. 