What do protien shakes do?

they are a quick convenient way of having some protein grams...if you want to gain weight you could do this ...get hold of a big coffee mug and fill it ¾ 's full then put a scoop of the powder on top ...mix with water with a spoon ...then have that 6 times a day in between your regular meals...you NEED to lift heavy and perform some form of cardio so these extra calories don't turn into fat ...

Protein shakes give you more protein in your diet if you struggle to get enough from food. It's basically powdered milk. It has no magical muscle building properties despite what advertisers might tell you.

It could help you gain weight as it contains calories. Anything that contains calories will contribute to weight gain. However, as they're typically quite low in calories (most are around 100 calories a scoop) they aren't going to be a big contributing factor in you gaining weight. If you want to gain weight, you need to eat more food.

Protein is what muscle is built from basically. Just drinking a protein shake without working out will probably do about nothing. But if you work out they'll supple plenty of protein to ensure the highest possible level of muscle growth.

Protein is a building material for muscles.It's a mild and legal way to get additional muscles with workout.

Well it gives you protein.