ICE Candidate
An IP address the browser offers for a WebRTC peer connection, before encryption.
ICE (Interactive Connectivity Establishment) is the protocol WebRTC uses to find a path between two browsers. Each browser gathers a list of candidate addresses it can be reached at: host (local network IP), srflx (server-reflexive, the public IP exposed by NAT), and relay (a TURN server's IP, used as fallback). These candidates are exchanged between the two browsers, and they pick the best one that works.
The srflx candidate is the privacy-sensitive one: it's the IP your ISP assigned you. A WebRTC leak happens when a website (or a tracking pixel) tricks your browser into gathering candidates and reporting the srflx back to a server the site controls.