Not a stupid question at all. I looked it up before I purchased the Cobra/Decepticon lithograph.

"This term describes general offset printing. This process is used by most print publishers today. The original painting is photographed and the image is burned into four plates for a full color printing process. The ink comes from a roller on a printing press. High quality lithographs use a very fine dot screen on acid free paper with fade resistant inks."

v.s. Poster

"A reproduction that is usually printed in unlimited quantities with a lower grade of paper and inks than limited- or open-edition prints."