Illustrator - Pathfinder Tool.

The Pathfinder Tool is one of the most handy features of Illustrator.

It is found in the Window menu.

Window > Pathfinder.

It's a good idea to have it open everytime you open Illustrator.

The Pathfinder makes it easy to perform tasks such as adding two shapes together or subtracting one shape from another. If you hover your curser over the Shape Modes and Pathfinders icons abox will pop up which tells you the function they perform.

Select the rectangle tool from the Tool Box.

Draw two shapes which overlap.

Using the Black Arrow (Selection Tool) select both shapes.

Click the various Shape Modes and pathfinders and see what they do.