Video Graphics Array has a resolution of 640 x 480 pixels with 16 or 256 colors, while a megapixel has a million pixels. VGA and megapixel measure different things. A VGA screen has as much resolution as a 0.3-megapixel image.
A computer monitor running at VGA resolution usually displays an array of pixels that has 640 rows and 480 columns. If you lower the resolution to 320 x 200 pixels, the monitor displays 256 colors. VGA is the lowest common denominator resolution that all computer screens support, which means that all computers can display the programs that use VGA, even though the aspect ratio in which they display it may not be optimal. When computers first boot up, they usually display in VGA resolution before the operating system loads. Computers also use VGA mode when they are in Safe Mode.
A megapixel is one million pixels. Digital cameras usually use megapixels to measure their resolution quality. They can also compare the quality of images that do not share the same aspect ratio. A camera with more megapixels can capture images in a higher resolution. A camera's megapixel rating is more important for printing photographs than for displaying them on a computer monitor. A monitor can clearly display a 1-megapixel photo, but if you print the photo on a 4-by-6 inch paper, it begins to appear blocky.