Since nobody else seems to want to tackle this one, I'll do my best. Protein is made up of amino acids. There are 20 different types of amino acids--a complete protein source will contain all 20. Free form amino acids are just what they sound like...individual amino acids in their free form...i.e. not bound together in a structured protein.
I personally don't see much if any benefit to taking free form amino acids. Your body breaks down protein into individual amino acids anyway. If you are eating complete proteins (think meats, eggs, dairy, etc...) there's really no need to supplement will free form amino's...at least not for bodybuilding purposes. There are medicinal benefits from taking certain individual amino acids. For example Lysine is generally believed to be helpful in limiting the severity of a herpes virus outbreak (cold sores, canker sores and the like).
Hope this helps!