It becomes part of the image. From now on, that line is a pattern of pixels. When you enlarge a bit mapped image, you will get a pixelated look. If you are planning to print out an image that was originally 3 inches on 3 inches as 6 inches by 6 inches, you will get a very pixelated look. One might use bit mapped graphics to edit digitized pictures.
Bit mapped graphics are usually easier to work with.
Bit mapped graphics tend to create larger files than object oriented graphics. There are some exceptions to that rule. Original bitmapped graphic Same image scaled up As you can see from these two pictures, when a bitmapped image gets scaled up, the detail is lost, as opposed to an object oriented drawing where no pixelation occurs.