The present perfect tense is used when a past action has a result in the present. That’s the simple definition, but let’s look at it in more detail.
I opened the door = Maybe the door is not open anymore
I have opened the door = The door is still open
5 Rules for Present Perfect
1. An action that started in the past and continues now.
I have lived in England for 20 years
2. An action that happened in a time that has not finished.
I have been to the supermarket twice this week.
3. A repeated action sometime between the past and now.
I have been to Japan twice.
4. An action that happened very recently in the past – we often use “just”
I have just lost my wallet.
5. An action when the time is not important and we want to emphasise the action
I have climbed Mount Everest.