I think I should answer in english... right?
This is a very special spanish grammar form. That "le" is a "pronombres reflexivo", and it give the sense of the action is heading an object.
For example "I help" I would say "yo ayudo", "I" is doing the action.
"I give you" in this case "you" is receiving the action. So in this case you have to use the "pronombre reflexivo" that correspond to "you" wich is "te" and it goes between who is doing the action and the action. So it goes like "yo TE ayudo"
However if you say "ayudo" it understood that is "yo" who did the action, so you dont have to say "yo", so you can say "te ayudo" and the meaning is complete.
in this phrase "Le dí las llaves" as Edgar said, the complete phrase would be "yo le di" meaning "I gave her", but you dont have to say "yo". Too much information eh?