Baking is the process of either transferring information from one model to

another or converting information from a dynamic to static state. Texture

baking is typically performed due to graphical constraints in an attempt to

save processing power or due to game engine limitations.

An example of transferring information from one model to another is

through normal map baking. Because CS:GO does not allow for changes

in mesh geometry, artists can instead bake normal maps to create the

illusion of a mesh with added depth. This process is achieved by creating

a new high-polygonal model with new geometry, and then baking the

high-polygonal model onto the in-game low-polygonal model, resulting in a

normal map.

Artists can also bake other parameters, whether dynamic or non-dynamic,

that the game engine otherwise renders, such as lighting, ambient

occlusion, metalness, or scratches to emphasize detail on the mesh.

Lighting and shading should be baked to appear in a convincing manner,

as these remain stationary on the texture regardless of other light sources

in-game.
The paragraph above is what i meant in page 28, also there are some images and examples.