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.

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).