The Sims Creator is a bonus program that comes with The Sims Deluxe Edition, compilations which include it, and The Sims Complete Collection. Despite its name, it does not create Sims; that still has to be done in Create a Sim. Rather, it's a tool for painting and modifying skins. It includes a "Face Photo Wizard" which can "Simify" a photo of a face by mapping it onto a head mesh and creating a BMP image the game can use. Any clothing or heads that are added through expansion packs can be accessed and modified in The Sims Creator.
Because it is a separate program, players who do not have Complete Collection will need to use Disc 1 of Deluxe to start it, regardless of what other expansion packs they have.