man provides manual pages for terminal commands

$ man git
# displays git man page
q # to quit

Useful Options / Examples

man -f <command> shows a list of related commands that match the keyword

$ man -f git
perlgit(1)               - Detailed information about git and the Perl repository
git(1)                   - the stupid content tracker
git-add(1)               - Add file contents to the index
git-am(1)                - Apply a series of patches from a mailbox
git-annotate(1)          - Annotate file lines with commit information
git-apply(1)             - Apply a patch to files and/or to the index
git-archimport(1)        - Import an Arch repository into Git
git-archive(1)           - Create an archive of files from a named tree
git-bisect(1)            - Use binary search to find the commit that introduced a bug

Manual sections

The numbers in parentheses next to the commands correspond to the manual section they are in:

The standard sections of the manual include:

1      User Commands
2      System Calls
3      C Library Functions
4      Devices and Special Files
5      File Formats and Conventions
6      Games et. al.
7      Miscellanea
8      System Administration tools and Daemons

e.g. man -f printf lists printf(1), and printf(3):

$ man 1 printf
# displays printf (as a command) man page
$ man 3 printf
# displays printf (as a stdlib fn) man page

Sections within a manual page:

NAME             Name of manual page
SYNOPSIS         A brief summary of the command or function's interface
CONFIGURATION    Configuration details for a device [Normally only in Section 4]
DESCRIPTION      An explanation of what the program, function, or format does
OPTIONS          [Normally only in Sections 1, 8]
EXIT STATUS      [Normally only in Sections 1, 8]
RETURN VALUE     [Normally only in Sections 2, 3]
ERRORS           [Typically only in Sections 2, 3]
VERSIONS         [Normally only in Sections 2, 3]
ATTRIBUTES       [Normally only in Sections 2, 3]

Man pages reference

$ man man
# displays the man pages for man
$ man man-pages
# displays information of manual sections and descriptions