As Staff I see peoples other nicks (I assume I am seeing all the nicks registered to a particular ip address?) when they join the server.

Is there a command to let me see them if they are already on, I thought whois might do it but it doesn't?

 

/clones [name]

will list all of the accounts that currently share IPs with [name].
By the way, it's not showing "nicks" it is showing their usernames.

Thanks goodly that is what I wanted.

What is the difference between user names and nicks?

 

4 minutes ago, matelo2 said:

Thanks goodly that is what I wanted.

What is the difference between user names and nicks?

 

The username is the account. All of their data is tied to the username and you must use the username when targeting them with commands. A nickname is something you can give to players which changes what their name looks like when they talk in chat.
For instance you could do /nick matelo2 ClassiCuber
And in chat if you talk it goes: ClassiCuber: Hi
But you still need to do /tp matelo2 as a command example.