Take, for instance, the following image. And the final image is 4 pixels by 4 pixels. Figure I.1 Demonstration of pixels. There are two ways in which computers can create graphics. One is with vectors and the other is with bitmaps or raster images.
Vectors use mathematical formulas to define shapes onscreen.
Adobe Illustrator uses this method. Indeed, a pixel without magnification is barely visible. There are 72 pixels square, for example, in every square inch of your monitor. This is important because this is how Photoshop creates images. In fact, this is how all digital images are created, viewed, and edited.