intro —
introduction to general commands (tools and utilities)
Section one of the manual contains most of the commands which comprise the
  BSD user environment. Some of the commands included in
  section one are text editors, command shell interpreters, searching and
  sorting tools, file manipulation commands, system status commands, remote file
  copy commands, mail commands, compilers and compiler tools, formatted output
  tools, and line printer commands.
All commands set a status value upon exit which may be tested to
    see if the command completed normally. The exit values and their meanings
    are explained in the individual manuals. Traditionally, the value 0
    signifies successful completion of the command.
man(1),
  intro(2),
  intro(3),
  intro(3lua),
  intro(4),
  intro(5),
  intro(6),
  intro(7),
  intro(8),
  intro(9),
  intro(9lua)
The Regents of the University
    of California, UNIX User's Manual Supplementary
    Documents, University of California, Berkeley,
    http://www.netbsd.org/docs/bsd/lite2/usd.html,
    June, 1993.
An intro(1) manual appeared in
  Version 6 AT&T UNIX.