An early networking protocol created by [Apple] Computer to allow easy file and printer sharing between their Macintosh comptuters. 
Originally transported over an RS422 serial bus (Localtalk aka printer cable networking) later Macs use Ethernet and even "AirPort" 802.11b/g.
Note that some switches and routers have been known to baulk at passing Appletalk packets over Ethernet.  Check with the manufacturer's specs for your model to see if Appletalk is supported.