The wildcards are * (asterix) matching zero or more characters and ? (query/question mark) exactly only one character
example of using a wildcard to ban would be if a group of bots joined your room with nicks libra23 libra24 libra25 libra26 you could ban the nicks
/mode #channel +b libra??!*@* would ban all of those nicks at once.
Example of the * ban would be /mode #channel +b default*!*@* would ban the following nicks default734, default25, default4511, default2, defaultabc.
* being used to replace multiple characters
There is many examples of wildcard bans but above is just a basic example of how they can be used.