State synchronization
A netcode model in which the server regularly broadcasts the world's authoritative state and clients interpolate between the snapshots.
In this model the server owns the truth. It simulates the whole world and periodically broadcasts snapshots of the state — positions, velocities, health — to every client. The client draws what it receives and fills the gaps by interpolating between two snapshots, a fraction of a second behind the server. The opposite is deterministic lockstep, where only inputs are sent and everyone computes the same world.
State sync is easier to make robust against cheating and diverging simulations, but it moves more data and needs tricks to hide latency: client-side prediction for your own player, server reconciliation when the prediction is wrong, delta compression to shrink the packets. The idea was spelled out early in Quake and the Source engine, and Glenn Fiedler's articles on networked physics are standard reading.