"Image Size" normally referes to the image dimensions in pixels such as 800px x 600px.
"Print Size" is the dimensions in inches or centimetres that you print that image to.
Now you can print that image at whatever size you choose (within reason), but the larger you print it, the more ‘spread-out’ will be the pixels and the lower the image quality.
If you print that image at 3.3" x 2.5" it will print at 240 ppi and be printed with as good a quality as you are likely to get from it. If you print it at 11" x 8.3" it will print at a mere 72 ppi and will look pretty rough…..