On DALnet, and quite possibly other IRC networks, CSOP - or Channel Service Operators, are a level of IRCop (IRC Operator) above normal operators and service administrators.
CSOPs have all the same access as the lower levels, and also the ability to deal with lost channel and nick passwords, and to freeze or close channels for abuse.
Most of the functionality of this isn't provided directly by the IRC server software, but by Operserv, another service within DALnet that provides extra functionality to operators.
Users shouldn't usually go to a CSOP directly, but direct their query to any IRCop via the normal methods (which on DALnet is via the channel #operhelp) and then, if appropriate, it will get passed on to a CSOP.