Commands are actions - they are things that the server will actively do. Contrast this with functions, which are (in general) things which change data and return the changed data.
If you need to change the database, you probably need a command. (A few functions, called 'side-effect functions' will also change the database.)
If you need to send information to a player, you probably need a command. To display things, commands. To backup the server, commands. To move something to another room, commands. Create a room or an object or a thing - you get the idea.
What commands are bad at is data manipulation. For that, you use functions.
|See Also: List_of_commands, Commands and compare with functions.|