Glossary of Terms – What Is Clone [MiniTool Wiki]
Clone refers to creating an exact same copy of the source partitions/disk by copying them to a destination disk/partition sector-by-sector.
Consequently the destination disk/partition possesses identical content as the original one. It is important to know that the cloning process will overwrite all the previous data on the destination partition/disk, so a backup in advance should be necessary if it contains any important data.
Unlike standard copying functions, disk cloning involves copying hidden and in-use files, and thus presents special challenges, as those types of files are typically not available for copying.
A disc cloning program must have device drivers or equivalent for all devices used. The manufacturers of some devices do not provide suitable drivers, so the manufacturers of disk cloning software must write their own drivers, or include device access functionality in some other way. This applies to tape drives, CD and DVD readers and writers, and USB and FireWire drives. Cloning software contains its own TCP/IP stack for multicast transfer of data where required.
The simplest method of cloning a disk is to have both the source and destination disks present in the same machine, and then use disk cloning software to help. For more information, you can read Clone Hard Drive with Best Disk Cloning Software.