Present Perfect
The present perfect tense has a number of uses.
1 We use it to talk about experience.
- I've worked in 6 different countries.
- Have you ever been to Australia?
- She's won many awards for her books.
When these things happened is not important - the focus is on the action/state, not when it happened.
NB If we say when we had the experience, we must use the past simple.
- I've visited Russia several times.
- BUT I visited Russia for the first time in 1992.
We can never use the present perfect with a time in the past.
- I have been to Spain in 2002.
2 We also use the present perfect to talk about things that are unfinished - unfinished states and unfinished time periods.
- I've known him since I was 11. (unfinished state)
I met him when I was 11. I still know him now. The present perfect is acting as a bridge between the past and the present.
- I've had this watch for almost thirty years.
- We've lived here since I was a boy.
- She's been to the cinema three times this week. (unfinished time period)
This week isn't finished yet - she may go to the cinema again.
- We've already had two holidays this year.
- I've eaten too much today.
3 A third use of the present perfect is to show the present result of a past action
- I've lost my keys.
He lost his keys some time in the past but the result - he can't get into his house - is in the present.
- John's broken his leg and he can't go on holiday.
- A storm has blown down the telephone lines. We're stuck here!