1. What is server fps? What does it mean? My server has low fps and almost no one lags and we have 70+ ppl. And yes my server.fpslimit is -1 what should it be to make it better? Or is -1 good?
     
  2. The servers FPS is how often per second the server will simulate world entities that are server-controlled.
    For example, the moving and thought of AI entities, such as bears, chickens etc.

    The more FPS you have, the better the AI will react to players and other events nearby, for example a server running at 10fps does not do such a good job at making AI attack players as quickly as a server running at 50fps.

    The FPS also includes reading the input from the servers console.

    As for the whole "I have 70+ people and no lag" - this isn't really affected by FPS as the rust server will just throw incoming data back out to clients that require it, this is most likely on a completely separate thread than any other game logic.