Agario Game Club is an Agario private server. The rules are just the same. Private servers are a unique opportunity to play on the fresh server first and to fix yourself at the top of the leaderboard.
How to Play
The goal of the game is to get the maximum points. Collect the color dots appearing everywhere on the map. Agario servers doesn't mean there're no opponents, there're a lot of them as on any agario server. Rules are the same, the bigger one absorbs the smaller one.
The bigger your cell becomes the harder to control it. It becomes slower. In this case to get an advantage in speed you've got to split into smaller cells. Also when splitting one cell is thrown out with a high speed. This can be useful to attack even smaller opponents. After a while cells merge into a big one again.
Agario private servers is a unique feature in the world of io games. No other games allow to setup independent server and run a game on it. Private servers are rather popular for pvp and solo play.