Whey Question

[Oh.2.B.Fit]

I have heard a lot of people talk about "Whey"
What do you do with it?
What brand do you get?
Is it good for you?
Why do you use it?
It is Whey Protien Powder right?
I almost bought vanilla.
Some had one carb, others had 11.
I have a lot of whey questions
I saw it today, and there were sooooo many to choose from.
Thanks for the help