Hello Lilia, The past simple tense indicates that an action has terminated completely in the past be it an hour ago , a day or a year or more . The present perfect tense indicates that the action has started in the past, usually the near recent past and extends to finish just right now in the present or a while ago in the recent past. Therefore when using the present perfect many times words like " just, now , already" are used. Examples: "I traveled to Paris last year." "I have just come back from Paris today." Notice that in the first example the trip to Paris is over with all its details and the person is telling about it as a past event that completely terminated. Whereas the second example tells a detail of a recent trip that has just finished today. So the whole action of traveling extended to the present ,although it started in the past ,be it a week or a month or more. "He finished his studies 2 years ago and is working now as a consultant." "He has finished his studies recently and will start to work as a consultant soon." In the first example the action of studying is fulfilled quite a long time ago (2 years) ,it is a full past action. In the second one the action is terminated too but in the very near past "recently" . "I have called him now to tell him that she arrived an hour ago." The call is recent, terminated in the very recent past * the moment the person is speaking (now)* . Her arrival is a past action * an hour ago* with no extension in the present. I hope the difference between them is clear through the previous examples:)

Here is an explanation from a grammar excercise: The present perfect is used when the time period has NOT finished: "I have seen three movies this week." (This week has not finished yet.) The simple past is used when the time period HAS finished: "I saw three movies last week." (Last week is finished.) --------- The present perfect is often used when giving recent news: "Martin has crashed his car again." (This is new information.) The simple past is used when giving older information: "Martin crashed his car last year." (This is old information.) ---------- The present perfect is used when the time is not specific: "I have seen that movie already." (We don't know when.) The simple past is used when the time is clear: "I saw that movie on Thursday." (We know exactly when.) ------------ The present perfect is used with for and since, when the actions have not finished yet: "I have lived in Victoria for five years." (I still live in Victoria.) The simple past is used with for and since, when the actions have already finished: "I lived in Victoria for five years." (I don't live in Victoria now.)

тю... это просто