/boot : Contains file that is used by the boot loader (grub.cfg)
/root : root user home directory. It is not same as /
/dev : System devices (e.g. disk, cdrom, speakers, flashdrive, keyboard etc.)
/etc : Configuration files
/bin → /usr/bin : Everyday user commands
/sbin → /user/sbin : System/filesystem commands
/opt : Optional add-on applications (Not part of OS apps)
/proc : Running processes (Only exist in Memory)
/lib → user/lib : C programming library files needed by commands and apps
/tmp : Directory for temporary files
/home : Directory for user
/var : System logs
/run : System daemons that start very early (e.g. systemd and udev) to store temporary runtime files like PID files
/mnt : To mount external filesystem. (e.g.NFS)
/media : For cdrom mounts.
