This object is completely distinct and independent of Account records that have been enabled for the partner portal.
describeSObjects(), query(), retrieve()
When you create a partner relationship between two accounts (when you create a Partner object and specify the AccountFromId), the API automatically creates two AccountPartner objects, one for the forward relationship and one for the reverse. For example, if you create a Partner object with “Acme, Inc.” as the AccountFromId and “Acme Consulting” as the AccountToId, the API automatically creates two AccountPartner objects:
This mapping allows the API to manage the objects and their relationship efficiently.