The difference between image and clone is both simple and confusing, because the terms are used interchangeably to mean different things.

Image and clone are two very confusing backup terms.
One reason is a deep, dark, dirty little secret of the industry: we don’t all agree on what these two terms mean. Quite literally, one person’s clone is another person’s image, and vice versa.
It gets confusing, and if you’re hearing different things from different people, that’s why.
I’ll provide what I believe are the most accurate and common definitions. Hopefully, that means you’re more likely to hear people agree than disagree with what I’m saying.

 

Source: What’s the Difference Between “Image” and “Clone”? – Ask Leo!