Josh,
Change Log is a feature that allows NAV to track Inserts, Modifications, Deletions to a specific field within a specific table. You can setup which tables and fields you want to track. If a change is made and you want to see when and who made the change, you can go to the Change Log Entries page and search for the field and table.
When the box is checked, Change Log is on and running. You can see which tables and fields by clicking Navigate/Tables.
Hope this helps.
Thanks,
Steve