The observe command can also be written as spectator. It enters you into spectator mode, and makes you play as no country (all countries are controlled by AI). Messages do not show, and the game is not automatically paused. This command affects how the country AI acts (as you are no longer playing as a country, meaning that country will have different actions every time based on AI decision), and as such, you should not use spectator mode as a means of finding out what will happen if the map were to be replayed from where you left off.
observe
observe
The only way this command can be executed. This toggles spectator/observe mode.
spectator
This command is an alias for the above command.