A shard is an active game-server world. Parties help players coordinate joins, travel, and rescues while the active server confirms each outcome. Joining or leaving a party does not grant Honour by itself; successfully helping somebody can.
Cross-server travel is a real transition between authoritative worlds, not a local cosmetic teleport. A rescue must still be completed after the rescuer arrives, and a Death Cache keeps its ownership and recorded Honour mood when it crosses between servers.