How is "Se" used?
I can't quite understand the usage of "Se." Can somebody explain this to me?
Gracias!To specify, I don't undestand "se" when it is used "in combination object pronouns."

Which pronouns? Le/Les, La/Las, Lo/Los? And why, exactly?
Is "se" contextual then? If it's not Le or La, how do I know the gender of the pronoun?

Some of the text examples are:
Nosotros se la traemos. - We give it to him/her/you.
No se la compro. - I don't but it for him/her/you.

It just seems strange to me. I don't understand!

Question

How is "Se" used?
I can't quite understand the usage of "Se." Can somebody explain this to me? 
Gracias!To specify, I don't undestand "se" when it is used "in combination object pronouns."

Which pronouns? Le/Les, La/Las, Lo/Los? And why, exactly? 
Is "se" contextual then? If it's not Le or La, how do I know the gender of the pronoun?

Some of the text examples are:
Nosotros se la traemos. - We give it to him/her/you.
No se la compro. - I don't but it for him/her/you.

It just seems strange to me. I don't understand!

Answer

Try to find your answer on these links. I think they can be very useful for you:

http://spanish.about.com/od/pronouns/a/introduction_se.htm
http://spanish.about.com/cs/verbs/a/passive_se.htm

Let me know if you need any help more.

Have a nice day.

Answer

Se has many uses in Spanish.
You have to use "se" with reciprocal verbs: For example: 
Se miraron, se besaron...  (Two or more people at the same time)

Other use can be the reflexive verb. Se trata de acciones que recaen sobre la propia persona.DucharSE, asearSE etc.

I hope to help you.