Let's compare 2 sentences "I have read 50 pages this week", "I read that book last year". The first one is a recent action that continues today and the 2nd is a finished action. Learn more below.
The past simple is used for actions or events that ended in the past, including the recent past. The present perfect is used for actions or events that are related to the present.
|I had three exams this week.(Meaning: As in the example above, the use of the past simple indicates that the week has just ended.)
|I have had three exams already this week.(Meaning: As before, the use of the present perfect indicates that the week has not yet ended)
Remember that we also use the present perfect for actions or events at an unspecified time in the past. If we want to limit the time of the actions or events to a period of time, we use expressions of time such as “last year”.
Note: Take note of the difference between the two first examples. The time expression “last year” is used in both, but in the second example, we have added the preposition “in”. In this example, with the use of “in”, we are identifying a period of time in which the action or event occurred, but not a specific time. On the other hand, if we don’t use the preposition “in”, “last year” indicates a specific time in the past.