Protein helps build muscle, but how does that work and how much does one need?
There are three types of muscle in your body - cardiac, smooth, and skeletal - but skeletal muscle is the kind that gets built up by working out. Muscles bulk up when micro-tears occur in the muscle during a workout, and then they get repaired, building up their mass.
Proteins are the building blocks of muscles, and amino acids make up proteins. Those amino acids are essential; the muscle growth only occurs when the amino acids are there to provide the material for new muscle.
So how much protein do you need? Well of course it's highly dependent on body type. It's recommended to take 0.8 g of protein per day to maintain muscle mass, that's about 63 grams for a person that weighs 175 pounds. Athletes, however, probably need a lot more than that. Use caution with those protein supplements though; excess protein can turn into fat.