Prior to version 10.7 (Lion), Mac OS X Server was a separate but.
MacOS Server, formerly named Mac OS X Server and OS X Server, is a discontinued, stand-alone server operating system by Apple Inc.It is also the name of its replacement software, an operating system addition, for macOS that provides additional server programs along with management and administration tools for iOS and macOS. Apple unveiled Mac OS X Snow Leopard at SAN FRANCISCO on June 8, 2009, Snow Leopard is an even more powerful and refined version of the world’s most advanced operating system and the foundation for future Mac innovation.