Good question. I would say that helping out involves an element of sharing someone's work. So, for example if you had a lot of dishes to wash, I could help you out by working with you. On the other hand, if you were trying to learn say, Quantum Mechanics and were completely lost, I could try to help you learn. (Actually, I couldn't as I don't understand the second thing about Quantum Mechanics, but you know what I mean :-)). It's a subtle difference,but I think a genuine one.

Help = basic action Help out = result.