Photoshop has given you the ability to draw vector paths using the Pen tool since version 2, but since version 6 you can create shapes, which are essentially filled paths. Photoshop achieves this wondrous feat with a special kind of layer called a shape layer, which is really a fill layer (explained in Chapter 6) with a vector mask to define the shape.
So why bother with shape layers? Why not just draw shapes on normal bitmap layers? Well, as discussed in Chapter 1, vector shape layers can do a few things that normal bitmap layers can't. For example, you can go back and edit a shape layer at any time — maybe you forgot to add a little star to a logo, for example—without losing any quality. You can also stretch and squeeze a shape layer as much as you want, again without losing quality or ending up with jagged edges.
Because shape layers are essentially fill layers, you can change the fill color with a couple of clicks, or even swap the color for a gradient or pattern, all without touching the shape's outline or causing any loss of quality. See Figure 5.1 for an example.
Naturally, there also are disadvantages to shape layers, otherwise nobody would use normal layers anymore. The main disadvantage is that, as vector-based layers, they're not great at storing real-world images with lots of subtle changes in color, such as photographs. For these types of images, normal bitmap layers are far and away your best bet. However, shape layers (and vector ...