"Le" or "Lo/La"?
I am confused as to when you're supposed to use "Le" and when you should use "Lo/La". I was told that Lo and La were direct object pronouns and that Le was an indirect object pronoun. But then I saw Le used in the sentence, "We hear him". That sentence translated to, "Le oímos". But in that sentence, isnt "him" the direct object? Is le used as a direct object pronoun when the object is a person? Could someone please explain this to me? 
2 Answers
It is not an easy thing to explain. In some areas of some countries, people use "le" instead of "lo" (= him) for complex historical reasons. This is called "leísmo", and academically it is somewhat discouraged, but accepted as long as it is used in masculine singular (i.e. never for "her"). A different story is when you are addressing someone as "usted", if you say "lo invito", it could be either "I invite him" or "I invite you" (formal), so people use "le" in this case for "usted", leaving "lo" for "him". This formal usage can be found in all countries.
This is actually native speakers breaking grammar rules (we do it in English all the time when you think about it) but it is commonly accepted. Where I live, it's pretty much encouraged. Le can take the place of lo as a direct object pronoun. This can be substituted when lo refers to a guy (him, usted) but not when it means "it".
It is less common to see this with les taking the place of los and even rarer to see it as le taking the place of la.
