it can be used topically (supposedly works similarly to minoxidil 2%).
it can also be taken orally. when using enough (3g to 15g, it can be a Human Growth Hormone stimulator). what that has to do with hair growth i'm not certain. i don't know if anyone's ever made the connection.
Arginine Pyroglutamate/Lysine (sold as one pill) is supposed to have a much stronger effect than Arginine, and is also supposed to be less toxic, because you don't have to take as much. Maybe 2 (1g Arginine Pyroglutamate, 1g Lysine) to 4g's total.