For past events that have some relevance / importance to the present.

• I have eaten so much today. I'm so full now.
• John lost his wallet; he still hasn't found it.

The Present Perfect: Meaning

With "ever" / "never" to talk about life experiences.

• Have you ever been to Moscow? No, I've never been there. 
• Have you ever eaten crocodile? No, I've never eaten crocodile!
  

Repeated actions that have been repeated up to the present time.

• She's watched Harry Potter 3 times!
• I've missed the bus 4 times this week.

The structure of sentences in Present Perfect

Affirmative (Positive)

I have been to China.

Form: Subject + have/has + verb (past participle)

Negative

I haven’t been to China.

Form: Subject + have/has + not + verb (past participle)

Question (Interrogative)

Have you ever been to China?

Form: Have/has + subject + verb (past participle)?

Your mobile phone has been ringing - (It rang for a while and has now stopped).

It has been snowing - (It has stopped snowing, but there is still snow on the ground).

John hasn’t been feeling too well recently - (He still doesn't feel well; it's ongoing).