Present Perfect Simple

The Present Perfect Simple is used:

To talk about an action which happened in the past,

but the extact time is not mentioned.

"I've already donde that"

To talk about a state which started in the past and continues

up tho the present.

"Mary has had her dog since September"

To talk about an action that happened in the past

and finished, but the results are obvius in the present.

"I've just finished my project"