The present perfect tense is used-
1- to express an action very recently completed. In such sentences, we often make use of the adverbial just:
I have just received your message. (received it just a little while ago)
The last bus has just left. ( left only a short while ago)
2- to express an action which began in the past and continues till the moment of speaking, or just finishes at the moment :
We have been at Ooty for two weeks. ( we came here two weeks ago and are still here)
I have waited for you for twenty minutes. ( The activity of waiting started twenty minutes ago but it is over now.