What they call "image based lighting" (rendering depth/normals into a separate image) is actually called deferred lighting / rendering. Image based lighting is

What they call "image based lighting" (rendering depth/normals into a separate image) is actually called deferred lighting / rendering. Image based lighting is when you use environment maps (like a cube map) for lighting rather than individually defined lights. Typically you precompute blurred versions of the environment map so you can sample it directly at various apertures.