Along the left side, you get to enter equations, points, etc. It has a keypad, so you can choose numbers, letters, functions, etc. These are all browser based, which makes it very easy to navigate on an Interactive White Board. I think teachers will love this.
As I mentioned before, a logged-in user can save graphs into a folder, share the link to the graph, or save an image of the graph in .png format. It even allows the user to tweet out the result of the graph.
Another great feature is the customizable settings of the graph. You have control over the x-axis, y-axis, scales, etc. You can even use pi as a label. Nice for trigonometry. Give the page a try. It is probably a page you'll come back to frequently.