The present perfect is for actions completed in the present: I have answered this question. The past perfect, or pluperfect is for actions completed in the past: I had answered this question by the time you arrived. The future perfect is for action completed in the future: I will have answered this question by the time you arrive.
The Simple Past is used to talk about an action or a situation or an event that happens in the past and is completely finished in the past and dated.
The Present Perfect it's used for an event that take place in the past but is still in progress in the present or have an effect on the present.
I give you an example :
I have eaten all the cake. (It is one action in the past; and the result is there is no more cake, so Present Perfect).
Another example more clear I think:
I lived in France for ten years. (Simple Past, action finished because now I live in another country, England for example).
I have lived in France for ten years. (Present Perfect tense, action beginning in the past but have an effect in the present, I'm still living in France).
Pentru fiecare timp ai învățat niște adverbe și formule.
Dacă o să le înveți, poți să le deosebești, și să pui timpul corect.