It is static, but it is not just light information, but information as to how light should react on the surface.
So, if the surface is flat, like the left plane, then you tell it with an image texture, that the light should react, as if it were the right plane:

This would be a Normal Map, there are other maps to be baked, and together they can create a stunning illusion of a highly detailed object, that actually is just a simple object..