These are the CMS components:
CMS server
CMS database
Web Author
Web Author .NET
Authoring Connector
Templates and placeholder server controls
Placeholder objects
Site Manager
Visual Studio .NET client
Publishing API
Site Deployment/SDAPI
Sample data
Database Configuration Application (DCA)
Server Configuration Application (SCA)
Content Connector (provided with the Microsoft Solution for Internet Business, or MSIB)
Essentially all the parts can be categorized according to four distinct purposes:
Managing and rendering content
Authoring content
Developing CMS templates
Managing CMS servers