The Linux File System

Most Unix-like systems like CentOS for example are folowing the FHS Standart (File System Hierarchy Standart). FHS describes permissions, filename and locations.

Directory Description
/  Root, Highest level in File system Hierarchy
/bin Command Binaries (grep, bash, shell, etc)
/boot Boot loader, linux kernel
/dev System devices (disks, optical drives, etc.)
/etc System configuration files
/home User/Users home directories
/lib System libraries
/media Removable media
/opt Software packages (often used for third-party packages)
/proc This directory contains system information
/run Process information
/sbin System binaries
/sys System Information
/tmp Temporary Files
/usr This directory provides another place for applications to live
/var Contains logs and other data that changes over time