The Gradient Tool works hand in hand with the
Gradient Palette. All you have to do is to select an object with the Selection tool. Then select the Gradient tool and start dragging it from the point you want the gradient to start to the point you want it to finish.
Et voilat, you have your gradient. You can apply gradients to fills and to strokes.
Before continuing through this tutorial, you need to create a gradient and then you can use it in the hands-on exercises in this tutorial on the Gradient Tool.
The next few steps cover the differences in applying a gradient with the Gradient tool instead of with the Gradient palette.