In general terms a “Server” is a single instance of the server files running. A “Physical Box” can run multiple server instances depending on the games demands and the hardware available.
Traditional low count game modes (2-32 players) you can typically run 2+ on a Windows Server [v2022].
- Intel Xeon E3-1270v5 processor (four physical 3.6ghz cores on QPI + hyperthreading + turbo->4ghz)
- 16GB DDR4-2133 ECC memory
World Size, Networked actor count, number of players etc has an impact on this.
Games like CS, Battlefield (1942-4), CoD 1-5, TF/TF2, Unreal Tournament, ran on traditional Game Server Provider (GSP) setups. Each physical box would run multiple 24/7 instances of games. These types of games do not move players to another server. They simply load a new map (rotation).
Epic Online Services and STEAM offer built in matchmaking services.
STEAMWORKS:
https://partner.steamgames.com/doc/features/multiplayer/matchmaking
Most hosting services like GameLift and PlayFab also provide MM services.
MS Azure PlayFab
AWS GameLift