An important concept relating to pixel or bitmap graphics is anti-aliasing. The need for this comes about because pixels are square. In a world where everything is made up of tiny squares, how do you represent things that are circular or diagonal? Pixel images rely upon anti-aliasing to smooth the edges on any diagonals or curves when shapes of different colors meet. Without anti-aliasing, images have lots of stair step jaggies as shown below.
In the above zoomed image, take a look at the edges. So for the anti-aliased edge, we see that it’s not just a single color white. There are numerous different whites that help that shape blend in to the background. But without anti-aliasing, we’re just using a single color of white, and we see this jagged effect on the curve.
Anti-aliasing prevents jagged selection edges by smoothing the color transition. And there are a few places in Photoshop where you will see the option to anti-alias. And whenever you see that option, you almost certainly want it turned on. Anti-aliasing also comes up when we work with type in Photoshop. When you work with type in Photoshop, you have the option to apply anti-aliasing to the type for smoothing of the edges of the type (sharp, crisp, strong, or smooth).