Internetwork Packet eXchange (IPX) is at the Network layer of the OSI model and is part of the IPX/SPX protocol stack.
Novell built on someone else's work, and are largely responsible for the use of IPX as a popular computer internetworking protocol as a result of their large marketshare of Network Operating System software (Novell Netware) in the late 1980s through mid 1990s. IPX usage is in stasis or decline as the boom of the Internet has made TCP/IP nearly universal. Computers and networks can run multiple network protocols, so almost all IPX sites will be running TCP/IP as well to allow for Internet connectivity. It is also now possible to run Novell products without IPX, as they have supported both IPX and TCP/IP for a few versions now.