The List Codes Dictionary is a grouping table that writes to the list code table, which drives the data viewed and edited in the Demographics, Lists and Opt In/Out tabs on a contact record along with other areas of the system. The top level GroupTypes for List Codes are seen in the next screen shot.
The List Codes most commonly used are Demographics, List Topics and Opt In/Out.
NOTE: MasterCodes created under List Codes can have Roles assigned to grant access on your website. However, these Roles are not removed if an end date is added to the List Code.