A ditto looks like a quotation mark — " — and it's used as you go down a list to indicate you're repeating whatever is above.
If your jellies and jams all cost $2.00, you can write $2.00 just once with the first item on your price list and " in the price column next to each item listed below. You can also use the word ditto informally to describe repetition: "I can't believe you wore those shoes. Ditto that hat." You may recognize Ditto as the aptly named son of the comic strip characters Hi and Lois; he’s the twin brother of Dot.