Deathmatch start
From DoomWiki.org
Deathmatch starts are positions defined on a level by the designer to designate where players start (and respawn) in a deathmatch game.
Normally, there is more than one such position on a level. One of them is chosen at random each time a player starts or respawns.
In the WAD file, deathmatch starts are denoted as Things. However, since they have no associated sprite, they are not visible.