Bonk.io is a game where the player is a ball and the objective is to either kill/outlast the other player by knocking them off the map or pushing them into a death object (usually black) or sometimes to capture a point (usually a white circle) by staying inside of it which will make the player's skin show up and get bigger until it reaches the edge of the circle in which the player will then win.
Bonk.io also has a chat where you can chat with other players in the server. Servers can be made by players for people to join where the host can choose maps and kick players. Player's can also play a quick match where you will join a random server that automatically picks random maps. Maps can also be created by players.