CENTOS Linux Filesystem Layout

Path	Description
/	Root Directory. Also contains all the key directories for the system.
/root	Root Home Area. Where all root's personal configuration and files are located.
/etc	Contains all important file configuration and settings for server applications.
/proc	A virtual representation of the status of the machine. It is a virtual filesystem used by the kernel to communicate with userland tools.Usually details of running system in the CPU can be seen using (/proc/cpuinfo), while the memory usage in (/proc/meminfo) etc.
/var	Short for variable. Which web contents (/var/www/html) and system log files (/var/log/) resides. Usually takes disk space quickly. That's why it is highly suggested to put this in a separate disk and also using Logical Volume Management(LVM) disk partition so that it will allows dynamic creation and resizing.
/boot	Contains the boot loader which are files that are needed to boot CENTOS. Includes configuration and kernel.Usually takes small partition size on the beginning of the disk.
/bin and /sbin	/bin Contains most of the user programs, while /sbin contains administration tools and privileged binaries.
/dev	Location for all devices files on the Linux system.
/home	Contains files and folders of users.
/lib	System libraries
/lost+found	Can be found in the root of ext2 or ext3 filesystem. Files and folders that are damaged, detached or missing from the system are restored here during disk checking (fsck) so that it can be recovered.
/media	Located on newer Linux systems which holds the mount point for removable storage such as USB drive.
/mnt	Located on older Linux systems
/usr	Contains the majority of user software. /usr/bin for regular user while /usr/sbin for root.
/opt	Usually used by large third party applications.
/srv	Contains files that are used by services. Most of the services use other location such as /var instead.
/sys	Contains information about the system.
/tmp	Contains temporary files and folder. It can be emptied once the system has been rebooted. It can be a perfect location if you have a temporary file to utilize. Take note that it is not safe to leave important files here.

To learn more just go to: https://en.wikipedia.org/wiki/Linux_Standard_Base