A. The Present Perfect is formed from the present tense of the verb ‘have’ and the ‘past participle’ of a verb: The Present Perfect Simple is have/ has + past participle.
B. We use the Present Perfect tense:
B1. for something that started in the past and continues in the present.
B2. for something we have done several times in the past and continue to do.
B3. We often use the adverb ‘ever’ (‘never’ for the negative form) to talk about experience up to the present.
B4. for something that happened in the past but is important at the time of speaking.
B5. It’s the (first) time something has happened.
B6. when someone has gone to a place and returned. But when someone has not returned we use have/has gone.
B7. Been (to) = visited