1. Present Perfect Continuous
My clothes are covered in paint. I have been
painting the fence.
In this case it does not matter whether something
has been finished or not. We are more interested in
the activity.
We also use the continuous tense to ask or say how
long (for an activity that is still happening):
E.g. How long have you been reading that book?

2. Present Perfect Simple
The fence was grey. Now it is white. I have
painted the fence.
In this case the important thing is that something
has been finished. ‘Has painted’ is a complete
action. We are interested in the result of the
activity, not in the activity itself.
We also use the simple tense to ask or say how
many times (for completed actions):
E.g. How many pages of that book have you
read?