Spectating
Also said as Spectator mode, Observer mode, Stream delay, Stream sniping
Letting people watch a match in progress, usually from a free camera with information that the players do not have. Most such feeds run on a delay.
Watching is how players learn and how esports exist. The delay matters, since a live feed lets a friend, or the opponent, see what the player cannot. Using a stream to find a player is called stream sniping.
Say it
“Add spectating on a two-minute delay, and a free camera with both teams' information. Show each player's view on demand, and let casters pause the feed without pausing the match.”
Where you’ve seen it
League of Legends makes spectators of matchmade games on Summoner's Rift wait three minutes, so what they see cannot help the players.
Not to be confused with replay
A replay is watching a recording after it is over. Spectating is watching it as it happens, even if you are a little behind.