This window contains most of the power tools for creating and manipulating pixels. A tool is selected when it's in black reverse. You can access tool variants by clicking and holding on the tool icon.
Lets take a quick run through the most used tools.
You may find it useful to refer to the Quick Reference card at the end of this handout. Click on the upper left square to set the foreground color. Foreground is the color you will get when you use brush-based tools or the paint bucket. The rainbow strip gives access to color families. Drag it to the Hue you want.