This is the priority value this virtual router uses in the master-election process, where higher numbers win, with two special reserved meanings: a master sending priority 0 to signal it's voluntarily stepping down so a backup should take over, and 255 reserved for the router that actually owns the protected IP address(es) itself. It's the primary lever for controlling which router in a VRRP group should normally be master under healthy conditions, and understanding the 0 and 255 special cases explains behavior that would otherwise look like a bug. Seeing a router announce priority 0 explains an otherwise-unexplained, clean failover to a backup router, distinguishing an intentional handoff from a failure-driven one.