Imaging hard drives is the process of copying it, bit by bit, to create an exact replica, in a way an "image" or 'snapshot'. The cloning part is the process of taking that "image" of a hard drive and placing copies of it on one or more other hard drives.
Clonezilla is free - a good tool for taking a snapshot of a system and reverting back to it later as a backup or to get things the way you once liked them.
HighlyRecommended!