The Custom tab(s) provide a variety of empty fields that custom information can be added to. The number of custom tabs/fields that are available are slightly different with each module.
Standard Custom Field Types
Last Modified Fields
Sometimes this tab also tracks the last user that modified the record and when it was modified.
Other Fields
These tabs also might contain some of the following fields depending on the module.
Note: Users can only edit this field in the GIS geodatabase environment. If the system is not integrated with GIS, this field will not be available.