The difference is the result of subtraction when two numbers are compared. It answers the questions

"How many more or fewer are there?" and "How much more or less is there?"

Martin wanted to buy a book on soccer. He found it for $19.95 at a local bookstore. When he checked online he saw that he could get the book for $14.50. How much less did the book cost online?
19.95 - 14.50 = 5.45
Thus, the book cost $5.45 less online.