Present Perfect

Use: actions and experiences in the past that are relevant now. Unfinished time.

Form: has/have + VERB (past participle form: driven, given, made, etc.)
Negative Form: has/have + not + VERB

We have lived in this house for twenty years. = Twenty years ago, we started living in this house. We still live in this house now.

He has climbed Mount Everest three times. = He climbed Mount Everest in 1988, 1999, and 2012. He might climb it again.

Sara has not completed the project yet. (negative form) = Sara started the project on Monday. Today is Friday, and the project is still not done.