The operators take netCDF files as input, then perform a set of operations (e.g., deriving new data, averaging, hyperslabbing, or metadata manipulation) and produce a netCDF file as output. The operators are primarily designed to aid manipulation and analysis of gridded scientific data. The single command style of NCO allows users to manipulate and analyze files interactively and with simple scripts, avoiding the overhead (and some of the power) of a higher level programming environment.
You can find a brief description on the module, with the command
module help nco
The documentation is available on the NCO webpage: http://nco.sourceforge.net/#RTFM
CINECA consultants can be reached through the addr: superc@cineca.it