Published by Mojang, Minecraft is a game that allows its players virtually unlimited creative and building authority in their 3D cube world.
A plugin (or a multiplayer plug-in) is an additive file for a Minecraft multiplayer server. Plugins are often used to change certain aspects of the game, such as adding user rankings, or the addition of a "factions" game mode. Plugins do not change the game itself, as a mod does.