The Free On-line Dictionary of Computing (30 December 2018):
Unix manual page
Unix man page
(Or "man page") A part of Unix's
extensive on-line documentation. To read a manual page from
the Unix command line, type:
e.g. "man ftp" (the section number can usually be omitted).
Pages are traditionally referred to using the notation
"page(section)", e.g. ftp(1).
Under SunOS (which is fairly typical), Section 1 covers
commands, 2 system calls, 3 C library routines, 4 devices
and networks, 5 file formats, 6 games and demos, 7
miscellaneous, 8 system administration. Each section has an
introduction which can be obtained with, e.g., "man 2 intro".
Manual pages are stored as nroff source files. Formatted
versions are also usually cached. Man pages for most versions
of Unix are available on-line in HTML.
Unix manual page: man(1).
Linux man pages (http://www.kernel.org/doc/man-pages/).
Solaris man pages (http://docs.sun.com/app/docs/coll/40.10).