A clan is a form of organization in the context of competitive online gaming (often esports). Clans primarily consists of players. Clans support one or multiple games. Their members play together in teams in these games. Members can have one or more roles. Some roles do not require the member to actually play any of the games that are supported by the clan, for example very big and famous clans have editors that do not have to play the games, even though it might be helpful. Clans often have a specific clan tag that is used by their members in games to be identified as members of a specific clan.
Clans in Agar.io[]
Agar.io clans often are focused only on Agar.io and do not support any other games. Usually all their members play Agar.io, no matter which role the members have. Typical roles are leader, co-leader and member. Agar.io clans usually use a single messenger/voice chat tool for communication between their members. Typically these are: Discord, Skype or TeamSpeak. Many Agar.io clans are - at least temporarily - open clans. Therefore anyone can join them without an application and without being tested. Agar.io normally aren’t professional - they have no regular income and their players do not have contracts and do not get salaries. Also Agar.io clans are pure online clans, they do not participate in offline events. Agar.io clans often use a browser extension such as Agar Tool or Legends Mod to make it easier to play as a team and to communicate in-game.
A list of well-known Agar.io clans can be found here.