CMS is used for content management (usually
internet/extranet/intranet) -
http://www.microsoft.com/cmserver/
SPS is used for portals and collaboration (usually extranet/intranet) -
http://www.microsoft.com/sharepoint/
They can be integrated with the Connector for SharePoint Technologies -
http://www.microsoft.com/cmserver/default.aspx?url=/cmserver/downloads/sharepointconnector