Photoshop CS6 Tutorial
How to Combine Shapes in Photoshop
Shapes can be added or subtracted. The intersection can be excluded or the only thing left.
Open a blank document in Photoshop (File > New). Set the size to 500 pixels by 500 pixels at 72 ppi.
Select the Rectangle tool. Set the tool options to Shape Layers and click-drag a rectangular shape.
To add to your shape, click the shape layer in the Layers palette and select the Combine Shapes from the tool options pull-down menu.
Using the Rectangle tool click-drag another rectangle. It is added to the existing shape.
To subtract from the base shape, choose Subtract Front Shape from the shape options menu. Draw a rectangle to create a hole.
The Intersect Shape Areas option creates a shape defined by the intersection. Draw a rectangle and notice that only the intersection remains.
Exclude Overlapping Shapes option creates a new shape that excludes any overlapping areas.