You should try to take Whey protein after a workout or a heavy exercise session. Particularly after a heavy weights session. Whey protein assists in muscle repair and speeds up muscle repair and consequently muscle growth. It needs to be taken regularly to have a decent effect. Many bodybuilders swear by it.
Whey protein is usually used by people who are either trying to gain weight, or who are trying to gain muscle. It is just another type of protein, and it is easy to add to most foods and drinks.