A clone is an exact copy of the hard drive, bit for bit, with each bit in exactly the same location as on the original, including the parts of deleted files that remain on the disk. This is as opposed to a copy which will back-up the files but only those that are ‘live’ and will copy onto the new disk in the order it copies.
You can use freeware such as Aomei Partition Assistant Home Edition to clone a disk. You just follow the instructions.
I hope that is clear enough? Please ask for more detail if it is not. Cloning a hard drive can also be done by a machine it will exact copies of the hard dive if you are setting up several machines that are the same it copies files programs,and the operating system a great tool to save you time.