Subimage

A subimage is an individual image in a sprite that can be edited by itself. it makes up the animation for a sprite when played in sequence with the other subimages in that sprite but cannot actually be animated itself.

Uses
Subimages save enormous amounts of time and are much more organised, they can be controlled through Gml and are extremely handy when animations are needed.

Buttons
Buttons can be made by placing 2 subimages in one sprite, the speed can be set to 0 and the button can be made to change subimage when the mouse has rolled over the sprite.

Events after animation
Because of all these controls, certain events can be executed after a sprite has cycled through its animation, this can be useful for certain things such as explosion cycles as you would only want it to play through once.