The host can decide where other players go or people can pick their own spots. If a player is not put in a spot then the game will randomly assign them a spot when the game starts. In a game where everyone is randomly placed players won't know where the other players are on different teams are until they scout them.
Why didn't you use your ships to protect against that late attack from red?
Can the guy who made the server decide where the civs go?
The host can decide where other players go or people can pick their own spots. If a player is not put in a spot then the game will randomly assign them a spot when the game starts. In a game where everyone is randomly placed players won't know where the other players are on different teams are until they scout them.