Everything, every piece of constantly running code, is always present inside of a loop which does something (ticks) every set amount of time. If something does not need to define a method for calculation or for creating an object from a class or setting things up in a larger library (E.G OpenGL) it will always follow this law.
this amount of time between ticks, or the amount of ticks per second, can be changed. Though not all games use this exact technology, *every* game which renders things in frames-per-second atleast *emulates* this technique to the point where it is effectively doing something big every XYZ amount of time, or CPU cycles.
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