The present perfect can be used when something started in the past and is still happening now. I have lived in Paris for 10 years. This example means that you started living in Paris 10 years ago and still live in the French capital city. So it is very important to use the present perfect when you want to express an ongoing action that started in the past and that is still true now. If you had used the preterit, it would have meant that the action is over. I lived in Paris for 10 years means that you lived in Paris in the past, but that you now live somewhere else.

You can also find the progressive, or continuous form of the present perfect. Not many differences with the simple one and quite common when you want to talk about unfinished situations, or stress the fact that the activity is continuing now.

Subject + have/has + been + Vbing

For example: I have been waiting for two hours. We have been living together for too long.

 

Or less common:

Alf-post-letters