An electronic image is composed of a bunch of little tiny dots. Count those dots and you get the pixel resolution - the width times the height - of an image.

The pixel resolution of a camera is the actual number of image sensors that record one dot of information. Therefore, a 768 x 504 camera resolution will yield an image 768 x 504 pixels, whichever way you look at it. On a monitor at 72 dots per inch, the image will be 768 X 504 (about 10.5 inches by 7 inches) and on a page printed at 720 dots per inch the image will be 768 X 504 (about 1 inch by 7 tenths of an inch).

However, you would never need to print an image at 720 dots per inch because printer resolution is yet another definition altogether. Although printers often advertise 720, 1440, or higher resolution - and the higher is indeed better here - they are talking about a different beast. You would never be expected to resize your image to that insanely high resolution. If you did, you would end up trying to print 500 MB files which would look exactly the same if printed at 250-300 dpi (image resolution).