The icons give you a few options of what you want to capture in your picture.
1st: Capture the active window. This includes the tabs at the top of the screen.
2nd: Capture the window. This is just in inside of the webpage.
3rd: Capture just a rectangular section (that you can specify).
4th: Capture a free hand region that you can draw yourself.
5th: Capture the full screen.
6th: Capture a scrolling screen.
To use this feature, have up on the screen what you want to capture. In the FastStone box click on the type of capture you want to do. When it is captured, it will open into a new screen and you can zoom, crop, cut, copy, draw, add a caption, make a decorative edge, resize, email, print or save the image you captured.