/bin – Contains the executable programs that are part of the Linux operating system. Also contains essential system commands (in machine-readable format, or “binary” format, which is what “bin” stands for), such as “ls,” “cp” (used to copy files), “mv” (used to move files to a different location), and so on. It also contains the Shell like bash, which is most likely the shell you are currently using.

/boot – Contains Information necessary for booting the system. It also contains the Linux kernel. If you list the contents of /boot, you’ll see a file called vmlinuz – that’s the kernel.

/dev – Contains all device files. Linux treats each device as a special file. All such files are located in /dev.

/etc – This contains configuration files of linux system. There are lot of things here, as an example few of them are stated below:
- initialisation scripts in /etc/rc.d subdirectory. Services, scripts those are required to start or execute when system boots up
- /etc/inittab: A text file that describes what processes are started at system bootup and during normal operation. For example, here you can determine if you want the X Window System to start automatically at bootup.
- /etc/fstab: This file contains descriptive information about the various file systems and their mount points, like floppies, cdroms, and so on.
- /etc/passwd: A file that contains various pieces of information for each user account. This is where the users are defined.
/home – Home directory is the parent to the home directories of users. For example: /home/neo

/lib – Contains library files, including loadable driver modules needed to boot the system.

/lost+found – Directory for lost files. Every disk partition has a lost+found directory.

/media – Directory for mounting files systems on removable media like CD-ROM drives etc.

/mnt – A directory for temporarily mounted filesystems.

/opt – Optional/Additional software packages copy/install files here.

/proc – A special directory in a virtual filesystem. It contains the information about various aspects of a Linux system. For example, “/proc/cpuinfo” has information about your computer’s processor, and “/proc/modules” lists kernel modules those are currently loaded in the system.

/root – Root users home directory.

/sbin – Contains administrative/system binary files. Commands such as mount, shutdown, umount, resides here.

/srv – Contains data for services (HTTP, FTP, etc.) offered by the system.

/sys – A special directory that contains information about the devices, as seen by the Linux kernel.

/tmp – Temporary directory which can be used for temporary files. Applications use this directory often, which can be accessed by all users on the system.

/usr – Contains subdirectories for many programs such as the X Window System.

/var – Contains various system/administrative files that changes frequently such as log, mail directories, print spool, etc.