The eight sections
A manual page is identified by a name and a section number, written grep(1). The number matters: the same name can appear in more than one section and mean something different in each.
1User commands
658 pages
Things you type at a shell prompt. If you are looking up a command, it is almost certainly here.2System calls
708 pages
The kernel's own entry points, called from C. read, write, fork, mmap.3Library functions
1,814 pages
Functions from the C library and other libraries. printf, malloc, atoi.4Devices and special files
36 pages
Device files under /dev and the drivers behind them.5File formats and configuration
281 pages
The format of a configuration file, rather than a program. crontab(5) is the file; crontab(1) is the command.6Games
1 page
Games and screensavers.7Overview, conventions, miscellany
449 pages
Conventions, protocols, character sets, and everything that is a concept rather than a program.8Administration and privileged commands
408 pages
Commands for running a machine, usually needing root. mount, systemctl, fdisk.
658 pages
Things you type at a shell prompt. If you are looking up a command, it is almost certainly here.2System calls
708 pages
The kernel's own entry points, called from C. read, write, fork, mmap.3Library functions
1,814 pages
Functions from the C library and other libraries. printf, malloc, atoi.4Devices and special files
36 pages
Device files under /dev and the drivers behind them.5File formats and configuration
281 pages
The format of a configuration file, rather than a program. crontab(5) is the file; crontab(1) is the command.6Games
1 page
Games and screensavers.7Overview, conventions, miscellany
449 pages
Conventions, protocols, character sets, and everything that is a concept rather than a program.8Administration and privileged commands
408 pages
Commands for running a machine, usually needing root. mount, systemctl, fdisk.