Latency
Also said as Ping, Lag, Round-trip time, RTT
How long data takes to travel between machines. Ping is the time there and back, in milliseconds, and part of it is simply the distance and the speed of light in glass.
You cannot program it away, only hide it. Everything else in this world is a way of hiding it, so the first thing to know about any netcode is how much latency it was built to survive.
Say it
“Put servers in Frankfurt, Virginia and Singapore, so that most of our players get under 60 ms of ping. Show the ping number in the corner of the scoreboard.”
Where you’ve seen it
Riot set out to give 70% of Valorant's players a ping of 35 ms, and got there by standing up servers around the world and building its own network backbone, Riot Direct.
Not to be confused with input latency
Input latency is the delay on your own machine, from button to screen. Network latency is the delay between machines. In an online game you feel both, added together.