The Cordial database is a single unified database of all contacts and is not partitioned by separate lists.
For example, if you imported List-A that had 100 contacts, followed by List-B that had 100 contacts that were different, you would now have 200 contacts in the database. However, if List-B had 50 of the same contacts as List-A, the net amount of contacts in the database would be 150.
To preserve the relationship of lists, Cordial provides a list data type to associate a contact with a list. When importing a file of contacts, it is possible to identify contacts to the list they originated from. Using Cordial's Audience Builder, you can then select all contacts that are on one list or multiple lists. So in the previous example where we had a net of 150 contacts in the database, we could still query List-A and List-B separately and get a count of 100 for each.
View the following articles for more information on lists and importing contacts: