imperfecto VS pretérito

Hello, can somebody please explain me the difference between imperfecto and pretérito tenses. When do we use eaither of them?

Thank you

anyone, please?

http://www.cuadernoscervantes.com/ele_52_preterito.html

It's quite complicated to translate it now. I will try to do it this weekend, I can't even think right now. So, till then, at least someone helps me out with the explanation of it!!!

Once I know is that the Imperfecto usually is used (or should be used) for actions in the past that last a period of time or where often. And that the preterito usually means something that happened once, or a specific number of times. IE:

Preterito:
Ayer fui a correr al parque.(it was yesterday, and didn't say how long I was running)
Cuando era niña, una vez visité París con mi padre. (I went to Paris with my father, just once in the past).
Fui tres veces a Londres en los últimos años (I went to london three times, it's an specific number of times)

Imperfecto:
Cuando era niña me gustaba jugar a las escondidas (it was like an habit)
De pequeña tomaba siempre un taxi para ir a clases de Valet. (an action doing often in the past)
Cuando era niña jugaba Voley(Ball) para el equipo local (it last a period of time, it wasn't once or an specific amount of times)

Well, I must lead to my bed. See you!!!

The main difference between these two tenses is that the Preterit expresses the end or completion the verb, whereas the Imperfect has no sense of completion. Sometimes, the usage of one or the other is indifferent from a grammatical point of view; thus, we can say Te veía desde la ventana, as well as Te vi desde la ventana. In both cases, the action denoted by the verb "ver" is already completed (it's past); in the first case, though, the speaker focuses (for whatever reason)on a progressive action; in the second instance, the Preterit expresses a specific moment of the completed past action.

As you see the use of the Imperfect can be translated as a progressive past To be + -ing verb. We use this same pattern too SER + GERUNDIO

Ex. leía un libro = estaba leyendo un libro (I was reading a book)

¡Xiurell, sos un genio!

jejeje

Te diste cuenta que dije "sos" y no "eres", definitivamente tengo el castellano de mi país muy metido en mi cabeza

Hey there, Thank you very very much for your explanations! I really do appreaciate your help and I am sorry for not dropping by earlier.
I don't have so much time to check the forum, that's why sometimes I might not answer to you straight away. Sometimes when I post an enquiry and there is no answer in a few days, I kinda forget to check it once again, as I have many things to do at the moment. But still, thank you very much for the help )) I understand the difference between those two now )))