Agar.io is a game where you start as a tiny cell and eat other smaller cells to become bigger and be the biggest in the server. You know your in the rankings if you have your nickname (you type a nickname to any name that you want) in the color orange that means your in the rankings. Some tips to know when you start is to mostly avoid the other cells because they are most likely to eat you. You should eat food that are lying around to become bigger and then start eating other cells. It is an addicting game but also fustrating.