UPF stands for "User Plane Function". It is a key component of the 5G core network architecture.

It handles the forwarding and routing of user data traffic between the access network (e.g., 5G base stations) and external data networks. And it performs various packet processing tasks, such as packet routing, packet filtering, and traffic detection.

The UPF ensures the appropriate QoS treatment for user data flows, and applies the necessary policy and charging rules for user data flows, as instructed by the Session Management Function (SMF).