One of the reason why JPGs are so common is because they incorporate compression. If you transfer an image from your phone to your computer, it will more than likely be in JPG format. JPGs (or JPEGs) are the most common pixel-based image file format. Most monitors will support over 24 million different colors so these pixels can be comprised of A LOT of different possible colors! Because pixels can be so many different possible colors, and there are so many of them in an image, pixel-based images do a great job of capturing photo realism. One image can be comprised of millions of different colored pixels.

On the right a small section of balooon blown up where you can see the individual pixels. On the left, you can see the picture of a balloon.