In the context of online multiplayer games like Eaglercraft, a "client" refers to an instance of the game running on a player's device, connected to the game server. Client selectors or management tools are used to handle multiple connections or instances efficiently, ensuring smooth gameplay, reducing lag, and improving the overall gaming experience.
It's crucial to be aware of the context in which Eaglercraft exists. The project is a third-party service that offers a free, browser-based version of a commercial game. As such, it occupies a legal gray area and is often considered a form of piracy.