Handing off Looks from Look Development to Lighting
The most standard use of Katana's Look Files is to describe what materials are needed for a given asset, such as a character, car or building, and which material is assigned to each geometry location. The Look File can also record any overrides such as modifications to shaders on particular locations, for example if a given object needs the specular intensity on a shader setting to a special value. The Look File can also record the shaders and assignments that are needed for a number of different passes, such as if you are going to do separate renders for passes such as the beauty pass, volumetric renderer.
The traditional workflow is that Look Development defines how each asset should look in all the different render passes required. They then 'bake' out a Look File for each asset, or multiple Look Files if there are a number of alternative look variants for an asset.
The Look File records this data in a form that can be re-applied to the 'naked' asset in Lighting. In Lighting the appropriate Look File is assigned to each asset. Downstream in the Katana graph, when you want to split into all the different, separate passes, you do a 'LookFileResolve', which actually does the work of re-applying all the materials and other changes to the asset that are needed for a given pass.