Mappings - or sometimes called Mapplets - are custom additions to the Delphix Masking Engine. During a service engangement Delphix Professional Services sometimes build such custom additions when specific masking requirements can't be implemented with the standard algorithm frameworks. Some of those custom mappings may be added to the product later which you'll find listed under the Mappings category. This menu item allows the user to upload the mapping received from Delphix Professional Services into his Delphix Masking Engine. Documentation of the specific Mapping is part of the service delivery.