How do I understand the "se" in "se lo explicas"?

Question

The full sentence is from a coursebook: "Si un compañero te pide que le expliques un asunto de trabajo que él no entiende cómo funciona... se lo expicas lo mejor que puedes." Why is it "se lo explicas" and not "le lo explicas"?

Answer 1

It is done for reasons of sound:

http://www.studyspanish.com/lessons/iodopro.htm

Whenever both pronouns begin with the letter "l" change the first pronoun to "se."

le lo = se lo

le la = se la

le los = se los

le las = se las

les lo = se lo

les la = se la

les los = se los

les las = se las

The reason for changing "le lo" to "se lo" is merely to avoid the tongue-twisting effect of two short consecutive words that begin with the letter "l". To demonstrate this, first quickly say "les las" and then quickly say "se las." See how much easier it is to say "se las?"

It isn't for reasons of sound. It is explained to you that way so that you can form that figure in your head. ;) - chileno, Aug 6, 2014

Personally I think it's done just to make learning Spanish even harder. - annierats, Aug 6, 2014

Thanks, that's perfect. I asked three native speakers at work (I'm in Chile) and none of them knew. - just4karns, Aug 6, 2014

It's just a personal pronoun used to passive sentences. Good luck with it. It could be a nightmare even for Spanish speaking people. - juanmelgar, Aug 6, 2014

Answer 2

Yes, when you have both, indirect pronoun and direct pronoun, remember:

Always first indirect pronoun If both start with "l", the indirect pronoun changes to "se" for singular and plural.

Don´t be confused with this "se" as indirect pronoun and the reflexive "se" or "se" in passive sentences. They are different.

Hope this helps!