In Unix-like operating systems, to make a filesystem available for access by attaching a named filesystem to the filesystem hierarchy at the directory specified (the mount point). The root filesystem is mounted on the root directory, "/" early in the boot sequence.
Filesystems are mounted either at boot, on demand by an automounter daemon, or by the user.
Other operating systems, such as VMS and DOS, mount filesystems as separate directory without any common ancestor or root directory.
Usually, the usage of the command is as follows:
mount [-t fstype] <device> <mount point>