The aspect ratio of an image is the ratio of its width to its height. The larger the ratio, the ‘wider’ the image; the smaller the ratio, the ‘squarer’ the image.
Print papers come in a range of sizes. Not only that, their proportions, or 'aspect ratios', are different too. Snapshots are usually printed on 6" x 4" paper, and traditional darkroom print sizes include 7" x 5" and 10" x 8" sizes still used today. You can naturally get larger sizes still, and these will depend on your photo lab.