Tick rate
Also said as Tickrate, Server tick, Update rate, Hertz
How many times a second the server works out what has happened. Anything that reaches it between ticks has to wait for the next one.
A higher rate means fresher updates and shorter waits, but less time for each tick and more data to send. Doubling it costs real money across thousands of servers.
Say it
“Run the match server at 60 Hz, which gives 16.6 ms for each tick. Measure worst-case tick time at 16 players, and if it goes past 12 ms, cut work before cutting the rate.”
Where you’ve seen it
Valorant runs its servers at 128 ticks a second and Counter-Strike: Global Offensive's official servers ran at 64, while Apex Legends runs at 20.
Not to be confused with frame rate
Frame rate is how often your machine draws a picture. Tick rate is how often the game's truth is updated. You can draw at 240 FPS and still be seeing a 20 Hz server.