The next two tools are the Paint Bucket Fill tool and the Gradient Tool.
Both these tools allow you to fill in selections. One with a solid color or pattern and the other with a gradient.
Layers are a way to easily modify or change your graphic design. They make adding special effects to specific parts of the design very easy to achieve. Also you can delete a layer and not affect the rest of your design.
In this very simple tutorial we’ll show you how to achieve a very similar Neural Density Filter (N.D Filter) effect to your photographs by using gradients in GIMP.