Overview
Mac OS X Server was provided as the operating system for Xserve computers, rack mounted server computers designed by Apple. Also, it was optionally preinstalled on the Mac mini and Mac Pro and was sold separately for use on any Macintosh computer meeting its minimum requirements.
Mac OS X Server is based on an open source foundation called Darwin and uses open industry standards and protocols. It included services and applications for file sharing, sharing contact information and calendars, schedule events, send secure instant messages, conduct live video conferences, send and receive email, contribute to and comment in wikis, publish a company-wide blog, produce and distribute podcasts, and set up websites.
Read more about this topic: OS X Server