What is a gamemode entity?

In common terms, gamemode entities are entities which are required for only certain gamemodes. Certain of those entities are:

Any other entities which affect the core gameplay are not considered as gamemode entities as the objective of the gamemode can be achieved without them or they can't be modified in the mapping process.

Entity explanation

The base entity only appears activated in the modes Capture, Regen Capture and Hold (plus it's variants).