Server.jar Link

: You don't just "open" it. Running it for the first time inevitably "fails" because you must manually open the eula.txt file and change eula=false to eula=true . It’s a rite of passage for every new admin.

: For a casual group of 10–15 players, you typically need 6-10GB of RAM and a processor with strong single-core performance. server.jar

At its core, server.jar is a lightweight executable distributed by Mojang Studios that lets anyone host a multiplayer world. : You don't just "open" it