When saving a photo, or image with continuous tone, it should be saved as a JPG. With a high resolution JPG, the picture quality matched the Photoshop file the closest, the image was not pixelated. As the resolution was decreased in a JPG, from high to medium or low, the picture quality decreased as well.  The high quality JPG was about twice as large of a file than the medium quality JPG, and the low quality JPG was an even smaller file.  Hard edge images, text and animations should be saved as GIF files.  These files may save large and small, it is determined by the dither and the amount of colors chosen to have show.  For PNG files, it works well when there is a transparent background.  The file was about the same size as the GIF file with a background, at a lower number of colors used.