A Logical Printer is a printer that is defined in IFS Applications, opposed to a physical / local printer that is specific to a computer running an IFS Applications client. Since the logical printer is defined in IFS Applications it's a printer which is available to all IFS Applications users. It's possible to configure rules that involves a logical printer - for a certain report or user a specific logical printer should be the default printer and so on. Scheduled printouts can only be printed to logical printers. It's the printers that are available from a server side point of view in IFS Applications.
An IFS Applications client like IFS Enterprise Explorer can also print to a physical / local printer, but in that case the actual printout is done from the client and since all users typically have different printers (locally connected or network printers) setup, it's not possible to have rules and logic in IFS Applications that uses physical / local printers.
There's obviously a connection between a logical printer and a physical printer device. This connection is made through a mapping in the configuration of one or several Print Agents. So when printing to a logical printer in IFS Application a printout is still produced by a physical printer hooked up to the machine running the Print Agent (either a locally connected or network connected printer). There are also a couple standard logical printers available in IFS Applications that are not used to print stuff on paper, but rather used to direct electronic information to other locations and/or trigger certain actions (i.e. SEND_PDF_TO_CONNECT, SEND_XML_TO_CONNECT, SEND_FULL_XML_TO_CONNECT, and NO_PRINTOUT). These special logical printers are never mapped to a physical device.