A man page is a form of software documentation usually found on a Unix or Unix-like operating system. Topics covered include computer programs, formal standards and conventions, and even abstract concepts. A user may invoke a man page by issuing the man command.
The man page for the sed utility, as seen in various Linux distributions.
Unix is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others.
Ken Thompson and Dennis Ritchie, principal developers of Research Unix
Photo from USENIX 1984, including Dennis Ritchie (center)
Promotional license plate by Digital Equipment Corporation, actual license plate is used by Jon Hall
HP 9000 workstation running HP-UX, a certified Unix operating system