A fabric edge node provides onboarding and mobility services for wired users and devices (including fabric-enabled WLCs and APs) connected to the fabric. It is a LISP tunnel router (xTR) that also provides the anycast gateway, endpoint authentication, and assignment to overlay host pools (static or DHCP), as well as group-based policy enforcement (for traffic to fabric endpoints).
From Cisco's guide, under SDA roaming - When a client on a fabric enabled WLAN, roams from an access point to another access point on a different access-switch, it is called Inter-xTR, like a highway. Intra is within intra is between. Like interstate highways. That's how I remember. https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/mobility.html