Tavuk, I think you misunderstood something.
FPS = frames per second, depends on your computer performance and game optimalisation, lower = worse, at about <20 causes some serious frames lss, making the game unplayable
Lag = the latency between your computer and the server connected to each other by internet, depends on your internet provider and server localisation, lower = better, at about >100 it starts to be really hard to play, at >200 you can't move straight without being pushed on the sides (causes an effect of "WUT I DONT KNOW WHY AM I GOING THE.... - you're dead) etc, at >500 you are lucker to stay on server, but if you stay... well good luck going out of spawn,