Difference between present perfect simple and past simple
Past simple is used with time expressions which refer to definite times. The time may be stated or understood. Choice between past simple and present perfect for recent events may depend on the attitude of the speaker. Ex: I’ve left my wallet in the car. I’m going back to get it. (the speaker may be about to return, and feels that the event is connected with the present). Ex: I left my wallet in the car. (the speaker may feel separated in time from the event, or be further away).
The present perfect always tells us something about the present. Ex: I’ve lost my key (=I don’t have it now). The past simple tells us only about the past. Ex: He lost his key (we don’t know whether he has it now or not). Do not use the present perfect for actions which are not connected with the present (for example, historical events). Ex: The Chinese invented printing. Shakespeare wrote Hamlet. Do not use present perfect to talk about a finished action in the past (yesterday, two years ago, in 1979, when I was a child).
We use the present perfect to give new information or to announce a recent happening. But if we continue to talk about it, we normally use the past simple. Ex: Oh! I’ve burnt myself! – How did you do that? – I touched a hot pan.
Difference between present perfect simple and present perfect continuous
We use the present perfect to say that the important thing is that something has been finished. That means we are interested in the result of the action, not in the action itself. We use the present perfect continuous when we are interested in the action itself, it does not matter whether something has been finished or not.
We use present perfect simple form to say how much we have done, how many things we have done, or how many times we have done something. Ex: Ann has written ten letters today. But we use present perfect continuous to say how long something has been happening. Ex: Ann has been writing letters all day.
We use present perfect simple for situations that exist for a long time (especially if we say always) and the situation still exists now. Ex: My father has always worked hard. But we use present perfect continuous for situations over a shorter period of time. Ex: John has been living in London since January.
Some verbs (be, have, know) are not normally used in the continuous. Ex: I have never been there. I have known him for ages. Other verbs (especially sit, lie, wait and stay) prefer the continuous form. Ex: I’ve been waiting for you for ages!