Since i don't know much about belts, please can someone explain it to me: how do you gain your belts in BJJ and what does it take to get one?
You gain your belt in Bjj usually when your instructor sees fit. Some schools have tests to become a blue belt or a purple belt, here's an example:
It obviously gets more difficult once you get past a blue belt, and gaining a purple, brown, black,etc are for a multitude of reasons, such as how much mat time you hvae, your ability to roll with higher belts, competition experience, etc. I would say very generally speaking if you practice Bjj 2-3 times a week here's what the belt system will look like:
8 months - 1 year: blue belt
2 - 3 years: purple belt
4 - 7 years: brown belt
8+ years: black belt