If you are going to be using a printer (or several printers) that are attached to your Koha server for producing statistical and operations reports, then you need to give each printer a name and tell Koha how to access it. You do this by telling Koha which print queue to use.
(In linux, each printer configuration in your printcap file defines a print queue. The default print queue is "lp," but if you use more than one printer you will have other queues, probably with names like "text" or "postscript." Tell Koha which printer queue(s) you want to use for printing reports directly from the server.)
Note that you can always print Koha screens directly to a printer attached to your workstation just by using your web browser's Print function.