Logging in on servers

[Taranis]

Recently I found out that you can log in on certain servers through authentication. Could someone explain to me exactly how this works? I know that you need to type "/login" when you get onto the server, but what do you type after that? (Is is "/login <username>" or "/login <password>", or something else?) I've looked around the forums and the wiki for info, but with no success.

Thanks

Edit: Btw, I'm trying to prevent impersonation, so I would really appreciate some help.

[dlh]

Authentication for Players