Conceptually, how does replay work in a game?

Question

I was kind of curious as to how replay might be implemented in a game.

Initially, I thought that there would be just a command list of every player/ai action that was t

Answer 1

The problem of having a consistent replay is the same (well, easier) like have a consistent multiplayer game.

As others mentioned before, replays in RTS games are stored by recording all input (that has an effect. Scrolling has no effect.) Multiplayer transmits all input, too

Recording all input not just a guess - there is a library for reading Warcraft3 replays with reveals this.

input includes timestamps for this answer.