A moving surface in a game that can be stood on. Can move back and forth, along a track, or in any other way that serves to kill characters just as often as it helps them.
A common component of platform-games. Jumping from platform to platform increases exponentially in difficulty when the movement of platforms is introduced.
This tag specifically refers to the translation movement of a platform in the game space; platforms whose only "movement" consists of disappearing into the background or rotating (thus altering the standing surface itself) are a different concept. Questions deal with things such as implementation, setting up paths, and scheduling the movements of whole systems.