system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do online games with many players in the same area ensure everyone sees the same things at the same time?

Title. I think I'm talking about latency/syncing but I'm not too sure.
gpt
Short answer: they don't. 

More in depth answer: the players(also know as clients) are constantly sending their actions(movement, attacks, etc) to the server(host) which processes the inputs and then sends updates back to the clients.

Normally this happens so fast that the human brain doesn't notice any inconsistencies(a "good" server response time is 0.01 to 0.1 seconds) but when there are delays in processing or connection(sometimes called lag) the host will process commands as they were received which can cause characters to "rubberband" or teleport around.

In a fast paced game(like an FPS) this is very noticeable, but in slower games the programmers will often just smooth over any rubber banding(after all, if you're chilling in town in an MMO does it *really* matter whether that player is *actually* standing there or walking away?)