An (often part of larger "Launchers" or "Eaglercraft Extras") is a utility designed to help players switch between different web-based versions and custom clients of Minecraft. Since Eaglercraft is a port of Minecraft Java Edition that runs in a browser, these selectors act as a hub for various game builds, such as 1.5.2 and 1.8.8 .
You might wonder, "I only play one version. Why do I need a selector?" Here are four compelling reasons: eaglercraft-client-selector