Footprints This category is specifically about footprints. It is nested inside of the "Layout" category, as it is closely tied to it. For all issues with the actual software (import errors, etc), please post under the "software" section.
Gerbers (GerbView) If you have issues generating or viewing your gerbers, you should post about it here. Also issues with file formates or understanding what gerbers should be used for.
3D Models This category is about the 3D modeling capabilities of KiCad, including the ability to import models of the components and export models of the entire PCB for external programs.