Cheatsheet....
/bin → USER BINARIES
/sbn → SYSTEM BINARIES
/etc → CONFIGURATION FILES
/dev → DEVICE FILES
/proc → PROCESS INFORMATION
/var → VARIABLE FILES
/tmp → TEMPORARY FILES
/usr → USER SYS RESOURCES
/home → HOME DIRECTORIES
/boot → BOOT LOADER FILES
/lib → SYSTEM LIBRARIES
/opt → OPTIONAL ADD ON APPS
/mnt → MOUNT DIRECTORY
/media → REMOVABLE DEVICES
/srv → SERVICE DATA