Disk space statistics is an important thing to know

Mounting

The linux file system combines all media disks into a single virtual directory.
Which means, if a new media disk is to be used, it should be placed in the virtual directory, which is called mounting.
In newer version of Linux, thijcls mounting process occurs automatically.

The $mount command

$mount

The $mount lists media devices currently mounted to the system.

From above image

• device_filename on /mount_point type filesystem_type (access_status)

So basically, the $mount command provides 4 pieces of information:

• The device filename of the media
• The mount point in the virtual directory
• The filesystem type
• The access status of the mounted media

/dev/sda2 on / type ext4 (rw,relatime,errors=remount-ro)

This shows that device file sda2 is mounted on root directory / which has a ext4 file type with access status inside braces.

Mounting a device

$mount -t type device directory
This mounts a given device of given type to the given directory
Here:

• type
  The filesystem type under which the device was formatted
  Eg. vfat for windows, ntfs for later windows, iso9880 for cd-rom filesystem etc

• device
  the location of the media device

• directory
  the location in the virtual directory (mount point)

Eg. to manually mount the USB memory stick at device /dev/sbd1 at location /media/disk, the command would be:
*$mount -t vfat /dev/sbd1 /media/disk

After it is mounted, the root user has full access to it.

Some additional option:
$-o
The -o option allows mounting file system with comma separated list of addional option such as;

• ro : Read only
• rw : Read / write
• user: allows ordinary user to mount
• check = none : mount without performing integrity test
• loop : mounts a file

Unmounting a file

$umount
The $umount command unmounts a file
*$umount [direcotry|device]
Eg. $ umount /home/rich/mnt

Also check:
https://unix.stackexchange.com/questions/3247/understanding-mount-as-a-concept-in-the-os