The five graphs around the edge of the page are all sine waves with different values for amplitude and frequency. The graph in the centre shows the combination of the five simple sine waves giving a more complex wave form.
You can experiment with the graphs by changing the values for amplitude(0-6) and frequency(0-25). When you press the plot button on any of the five sine wave graphs a new sine wave and a new combination wave with be drawn.
(Note that this page uses Javascript which may not work with some browsers.)