The privileged mount system call is used to attach a file system to a directory
of another file system; the unmount system call detaches a file system. When you
mount another file system on to your directory, you are essentially splicing one
directory tree onto a branch in another directory tree. The first argument to mount
call is the mount point, that is , a directory in the current file naming system.
The second argument is the file system to mount to that point. When you insert a
cdrom to your unix system's drive, the file system in the cdrom automatically
mounts to /dev/cdrom in your system.