TPS

TPS, short for Ticks Per Second, is a measure of how fast Minecraft mechanics such as redstone and farming run at. If a server's TPS is low, this causes what players call "server lag" which causes for normal functions of Minecraft to malfunction.

TPS should not be confused with FPS, Frames Per Second, which is the measure of how fast the player's computer is rendering the game of Minecraft entirely, while TPS is usually recognized as the FPS of a server, in which measures the speed of how fast the server renders Minecraft.