The present perfect simple is used to discuss events that have just been completed at the moment of speaking.
Q) Have you done your homework?"
A) "Yes, I've just finished it."
It is often used to suggest that a past action still has an effect upon something happening in the present.
"The pound has fallen against the dollar."
It is also used to discuss unfinished time.
Q) Have you done your homework today?
A) No, I haven't done it yet.
Note - You are talking about today and today isn't finished, so you may do your homework later!
Q) Have you ever been to England?"
A) "Yes I have."
Note - You are talking about something that has happened in your life and your life isn't finished!
You can also use the present perfect to discuss something from the past but you don't want to say exactly when.
Q) "Are you learning any languages?"
A) "Yes, I've begun to learn English."