Target mappings are technical objects used by Campaign in order to deliver messages. They contain all the technical settings required to send deliveries (addresses, phone numbers, blacklist indicators, additional identifiers...).
Administrators can access target mappings in the Administration > Application settings > Target mappings menu.
Target mapping creation or modification is possible to cover specific needs. In any case, their targeting dimension should always correspond to profiles (nms:recipient table). For more on targeting dimensions, refer to this page.