In the Linux file structure files are grouped according to purpose. Ex: commands, data files, documentation. Parts of a Unix directory tree are listed below. All directories are grouped under the root entry "/". That part of the directory tree is left out of the below diagram. See the FSSTND standard (Filesystem standard).
root - The home directory for the root user
home - Contains the user's home directories along with directories for services
bin - Commands needed during bootup that might be needed by normal users
sbin - Like bin but commands are not intended for normal users. Commands run by LINUX.
proc - This filesystem is not on a disk. It is a virtual filesystem that exists in the kernels imagination which is memory.
1 - A directory with info about process number 1. Each process has a directory below proc.
usr - Contains all commands, libraries, man pages, games and static files for normal operation.
bin - Almost all user commands. some commands are in /bin or /usr/local/bin.
sbin - System admin commands not needed on the root filesystem. e.g., most server programs.
include - Header files for the C programming language. Should be below /user/lib for consistency.
lib - Unchanging data files for programs and subsystems
local - The place for locally installed software and other files.
man - Manual pages
info - Info documents
doc - Documentation
X11R6 - The X windows system files. There is a directory similar to usr below this directory.
X386 - Like X11R6 but for X11 release 5
boot - Files used by the bootstrap loader, LILO. Kernel images are often kept here.
lib - Shared libraries needed by the programs on the root filesystem
modules - Loadable kernel modules, especially those needed to boot the system after disasters.
dev - Device files
etc - Configuration files specific to the machine.
skel - When a home directory is created it is initialized with files from this directory
sysconfig - Files that configure the linux system for devices.
var - Contains files that change for mail, news, printers log files, man pages, temp files
lib - Files that change while the system is running normally
local - Variable data for programs installed in /usr/local.
lock - Lock files. Used by a program to indicate it is using a particular device or file
log - Log files from programs such as login and syslog which logs all logins and logouts.
run - Files that contain information about the system that is valid until the system is next booted
spool - Directories for mail, printer spools, news and other spooled work.
tmp - Temporary files that are large or need to exist for longer than they should in /tmp.
catman - A cache for man pages that are formatted on demand
mnt - Mount points for temporary mounts by the system administrator.
tmp - Temporary files. Programs running after bootup should use /var/tmp.