Since what used to be called Privileged Account Management (PAM) has been named Privileged Identity Management(PIM), Privileged User Management (PUM), Privileged Account Security (PAS), and a lot more by the different vendors out there, the common abbreviation has become PxM to cover everything and a little more.
Basically PxM is about managing and monitoring generic accounts, privileged personalized accounts, (SSH) keys, privileges, removing administrator privileges, and so on. There are many articles and postings out there, that explain in detail, what is meant and what can be done.