What is the whitelist on a Minecraft server?

What is the whitelist on a Minecraft server?

Is like an invitation list you don't stand on it you can't get in

Only the players who are on the whitelist, if activated, can enter the server.

Something like a guest list. Only players that have been added can join the server

A list on which you can write players who can then enter the server.

All other players can't then go to your server.