When speaking of image processing, we often mean using a computer to modify bitmap images taken with a digital camera or scanned images. To modify such images, you usually need to install an image-processing program on your computer. There are many programs for image processing, and if you learn how to use one, you will be able to use most of them.
With many bitmap and vector graphics programs, you can combine bitmap images and vector graphics into one. This is why you should know the basics of both techniques.