Oper only:
==========
+a - admin        - Admin status. Can for example see IP addresses in "STATS c"
+b - bots         - See bot and drone flooding notices
+c - cconn        - Client connection/quit notices
+d - debug        - See debugging notices
+e - external     - See remote server connection and split notices
+f - full         - See auth {} block full notices
+F - farconnect   - See remote client connection/quit notices
+H - hidden       - Hides IRC operator status to other users
+j - rej          - See rejected client notices
+k - skill        - See server generated KILL messages
+l - locops       - See LOCOPS messages
+n - nchange      - See client nick changes
+s - servnotice   - See general server notices
+u - unauth       - See unauthorized client notices
+y - spy          - See ADMIN, LINKS, MOTD, STATS, TRACE notices

Servers/Services:
=================
+S - ssl          - Client is connected via SSL/TLS
+W - webirc       - User is connected using a webirc gateway
+r - registered   - User has been registered and identified for its nick.
+o - oper         - IRC operator status

*:
==
+D - deaf         - Don't receive channel messages
+G - softcallerid - Server Side Ignore for users not on your channels
+g - callerid     - Server Side Ignore (see modeg.txt)
+i - invisible    - Not shown in NAMES or WHO unless you share a channel
+p - hidechans    - Hides channel list in WHOIS
+q - hideidle     - Hides idle and signon time in WHOIS
+R - regonly      - Only registered clients may message you
+w - wallop       - See server generated WALLOPS

Channel Modes:
==============

+b - ban          - Channel ban on nick!user@host
+c - noctrls      - Prevent users from sending messages containing control codes to the channel
+C - noctcps      - Prevent users from sending CTCPs to the channel
+e - exempt       - Exemption from bans
+h - halfop       - Half-Op status
+I - invex        - Invite exceptions, nick!user@host does not need to be explicitly INVITE'd
                    into the channel before being able JOIN
+i - invite       - Invite only
+k - key          - Key/password for the channel
+l - limit        - Limit the number of users in a channel
+m - moderated    - Users without +v/h/o cannot send text to the channel
+L - extlimit     - Channel can make use of the extended ban list limit. Can be set only by irc-operators,
                    servers and services.
+M - modreg       - Unregistered/unidentified clients cannot send text to the channel
+N - nonickchange - This will prevent any user who isn't opped or half-opped (+o/+h) from changing their
                    nick while in the channel.
+n - noexternal   - Users must be in the channel to send text to it
+o - chanop       - Full operator status
+O - operonly     - This mode will prevent anyone who hasn't obtained irc-operator status from joining the
                    channel. Can be set only by irc-operators, servers and services.
+p - private      - Private is obsolete, this now restricts KNOCK, and can be set at the same time as +s.
+r - registered   - Channel has been registered. Can be set only by servers and services.
+R - regonly      - Only registered clients may join a channel with that mode set
+s - secret       - The channel does not show up on NAMES or LIST or in the
                    WHOIS channel list unless you are a member of the channel
+S - sslonly      - This mode will prevent anyone who isn't securely connected via SSL/TLS from joining
                    the channel.
+t - topic        - Only chanops and halfops can change the topic
+u - hidebmasks   - Hides +b/+e/+I mode changes and lists to everyone except channel ops, and
                    half-ops (+o/+h)
+T - nonotice     - Users without +v/h/o cannot send NOTICEs to the channel
+v - voice        - Can speak in a moderated channel, and is exempt from flood restrictions