The Options palette lets you control how the selected tool acts. Above is the options palette for the Selection tools and Brushes Tool. The selection tool options allow for selection type, meaning the shape (rectangle, circle, ellipse, and so on), mode (adding, replacing or subtracting from the selection), feather (feathers or "softens" the edges) and anti-alias (smoothing the outer edge of a selected area to avoid "jaggies") The selection tool's options first icon allows for a custom selection bringing up a dialog box where you enter the exact spot on the image to apply the selection size.
If you switch to the Paint Brush tool, you will notice that the options differ greatly from the Selection tool. From the Options palette you can control the shape and size of the brush tip, in addition to any other personal preferences you might have. Each tool's options will be covered in more detail as you progress through these lessons.