A whitelist is a list or register of entities that, for one reason or another, are being provided a particular privilege, service, mobility, access or recognition. Whitelisting is the converse of blacklisting, the practice of identifying entities that are denied, unrecognised, or ostracised, and the term "whitelist" was formed by back-formation from "blacklist".
Read more about Whitelist: Email Whitelists, LAN Whitelists, Program Whitelists, Application Whitelists