On enabling this option the URL (address you see in the address bar of your browser) will change to longer unique URL which will hold the whole graph data (coordinates) and other settings. After plotting a graph you can copy and paste that 'Friendly url' to any other site, then that link will directly open the plotted graph along with your other preset graph settings.
You can use this for both coordinate plotting and function plotting mode.
Note:- If you are using coordinate plotting mode and have large number of points to plot (about 150 or above) then, this feature might not work in Internet Explorer because of it's limitation.