Many printers have built-in Ethernet or Wi-Fi interfaces so that multiple computers can connect to them at once over a network. However, networking capabilities typically increase a printer's price, and some of the most popular (and least expensive) printers have only a USB connection, which normally means they can be used by the computer they're plugged into.
The Mac OS X printer-sharing feature lets any Mac with a connected printer function as a print server — accepting print jobs from any other Mac on the network and directing them to the printer, with the end result being the same as if the printer were directly connected to the other Mac.
Printer sharing presupposes that you've connected a printer to your Mac and configured it in the Print & Fax pane of System Preferences. As long as you can print from your own Mac to a printer directly connected to it, you're all set to enable printer sharing. (If you haven't yet configured a printer and need help doing so, open the Print & Fax pane of System Preferences and then choose Help Print & Fax Help for complete instructions.)
With at least one printer configured, you can share it by following these steps:
Choose System Preferences to open System Preferences and then click Sharing to open the Sharing pane.