MOSS is the integration of WSS 2.0, SharePoint Portal Server (SPS) 2003, and Content Management Server (CMS) 2002. Each of these products has its strengths:
WSS offered companies the opportunity for their employees to manage their documents and collaborate in a new way.
SPS 2003 allowed companies to create a central entry point for all of their internal WSS 2.0 sites.
CMS 2002 was a product to enable companies to create public-facing Internet sites.
MOSS brings all of these technologies together into a single product that allows companies to standardize sites on a single platform for all of their needs.