1 User Commands
Commands that can be run from the shell by a normal user (typically no administrative privileges are needed)
2 System Calls
Programming functions used to make calls to the Linux kernel
3 C Library Functions
Programming functions that provide interfaces to specific programming libraries
4 Devices and Special Files
File system nodes that represent hardware devices or software devices
5 FIle Formats and Conventions
The structure and format of file types or specific configuration files
6 Games
Games available on the system
7 Miscellaneous
Overviews of miscellaneous topics such as protocols, filesystems and so on
8 System Administration
Commands that require root or other administrative privileges to use