bin: binary, where programs live

etc: where configuration files for different system programs and utilities is

boot: where boot files is (the operating system itself)

cdrom: CD mount point

dev: pseudo entry that operating system puts there to interact with devices

lib: librarys for programs

media: media mount point

mnt: removeable media mount point or others

opt: options software

proc: pseudo entry that store process related data

root: roots home directory

run: where temp data stored

sbin: system binary for system programs

sys: pseudo entry that store system data

temp: where temp data stored

usr: where user related data stored, user accessible binary

var: any variable data (e.g. log)