A homebrew setting is a setting created for a specific group either by that group's GM or by the group as a whole, and which is used for the group's campaign instead of the default setting of the role-playing game that they are playing. A homebrew setting incorporates elements and changes not present in the original game. The term is generally used for settings that are largely original, rather than existing published settings to which homebrew changes have been made, but that is not an absolute rule.
Because generic role-playing games have no default setting, homebrew settings are common among players of such games.