Top level root directory

/boot

Keeps booting files.

/root

Home directory of root user

/home

Home directory for all users except root

/bin, /usr/bin

Contain program files (basic commands) used by non-privileged users

/sbin, /usr/sbin

Contain program files (basic commands) used by super user (root)

/dev

Keeps list of available devices (hard disk, cdrom, pen drive).

/etc

Contain basic linux configuration files (user database, network configuration etc).

/lost+found

Contain orphan files

/mnt

Contain mounting point

/proc              

Contain system start information which is directly handled by kernel of Operating System
(example: hard disk, CPU, RAM, Cache etc)

/tmp

Keeps temporary files

/usr

Keeps programs and data available to all users.

/var

Contain variable data, include log files and print spools etc on linux servers. or contains database of the server

/media

Mount point of removable devices like CDrom, pen drive etc.

/mnt

Temporary mount point for everything