The Gradient Tool applies a solid colour or colour gradient to an object's fill or stroke.
Although you can use the Gradient Tool to apply solid colours, its true power lies in its ability to apply and modify linear, elliptical, radial, and conical gradients.
You can also apply bitmap fills to objects, allowing you to add a bitmap image from an external source (like a pattern or texture) which can then be transformed on the object.
The following settings can be adjusted from the context toolbar: