There is a lot of information here, probably too much for those truly unfamiliar with programming. Raster graphics describe an image as an array of colored pixels. A 512x512 raster image displays with a size of about 7 inches by 7 inches on a typical monitor. Vector graphics describe an image independent of the resolution of the final rendering device. When this is plotted on a 600 dpi printer it will look much smoother than the same graphic rendered on a monitor.
Raster graphics are the only reasonable choice for photos and satellite images.
Raster graphics cannot be converted back to vector graphics. An exception to that statement might be that certain compressed image formats, PNG for example, identifies pixels of the same color and describe a region to fill with the same color, rather than specifying a color for each pixel. But the PNG compression still specifies the raster image exactly. Circles are still jagged no matter what the resolution of the printer. Here we will make portable pixel map files as our prime example of raster graphics.