The Mac mini is a desktop computer made by Apple. The most current version of the Mac mini was released in October 2018. It is popular because of it's small, yet powerful design.
Apple released the Mac mini as the only desktop computer that didn't come with a monitor, keyboard or mouse and is the first Apple computer to come with an HDMI port that would allow users to connect a television which gives it the capability to become a home theatre server.
Apple released a server configuration in the early 2010's but discontinued it in 2014. There are rumors of a new Mac mini upgrade that would reintroduce the Mac mini as a server option for homes and small businesses but as of now there is no way of turning a Mac mini into a server.