User modes allow you to control a variety of things while connected to IRC. They can be used to control how easy it is for other users to find you, what information you see from the IRC server, and who can send you private messages.
DALnet currently has 5 user modes that can be set by yourself, and 2 that can only be set by the server or NickServ.
All modes can be set by preceding with a plus (+) and unset by preceding with a (–)
Modes can also be combined, e.g. /mode nickname -s+C
Only allows private messages from users that are in one of the same channels as you.
/mode Fred +C
Known as ‘invisible’. Prevents people from finding you by your hostmask/IP unless they know your nickname.
This is a default mode that is set by the server when you connect, although it can be unset.
/mode Fred +i
Indicated you are using and have identified to a registered nickname using NickServ.
If a user has identified to the nickname, a line will be added to their /whois.
This mode can only be set by services, and cannot be unset.
Fred is email@example.com * Super Fred Fred is on @#Fred Fred is on irc.dal.net Fred has identified for this nick
Allows only private messages between users that have identified to their nicknames, and are have the usermode +r.
This mode does not prevent you seeing messages in channels, only PM’s/Queries.
/mode Fred +R
Shows you generic service messages and information about oper kills.
/mode Fred +s
Set by the server when you connect using a secure connection (SSL).
This mode cannot be unset.
Fred is firstname.lastname@example.org * Super Fred Fred is on @#Fred Fred is on irc.dal.net Fred has identified for this nick Fred is using a secure connection (SSL)
Wallops are network wide messages sent by IRC Operators (staff).
Wallops are now rarely sent on DALnet.
/mode Fred +w