PRESENT PERFECT

Main uses:

1) Past actions with results/consequences in the present.
Paul has eaten all the cookies.
When was the action done? In the past: a few minutes ago/yesterday.
Consequence? There is no cookie left. There is nothing left for me.



2) Actions which began in the past and are still in progress.
Paul has lived in London for 10 years.
When did it start? 10 years ago.
Is it finished? No, it isn't. Paul is still in London. He lives in London.



SYNTAX: HAVE (or HAS with he/she/it) + PAST PARTICIPLE
I have done my homework. She has done her homework (verb: do)



NEGATIVE:
I have not done my homework. = I haven't done my homework. She has not done her homework. = She hasn't done her homework.