First Hop Redundancy Protocol (FHRP)
A computer networking protocol which is designed to protect the default gateway used on a subnetwork by allowing two or more routers to provide backup for that address; in the event of failure of an active router, the backup router will take over the address, usually within a few seconds. Credit: Wikipedia
”First Hop” refers to the fact that the default gateway in any network is the first hop, i.e. the first router to whatever destination outside the network a given host is sending traffic to.