The weird pencil shape in curves

[Adooby-doobie]

Hello everyone

I think I might be pressing some weird button that toggles on a pencil and my curves don't seem to follow their route. How is it toggled on? And how to toggle it off? But most importantly what does it do? 
I couldn't capture it with the screenshot as it disappears when I hit the screenshot button.
Please help

Thanks

[Warren Heaton]

The pencil allows us to draw to modify the curve instead of using edit points to do so.  It's common to follow up drawing the curve with clicking the "Smooth" button.

To completely reset the Curves and try again, click the blue "Reset" text at the top level of the effect. 

If you like the results but would like to try something different, hide the first  instance of Curves and apply the effect again.