What does the "make screencast" button do? In the info view header, under Window there is an option to "Make Screencast".



It's tooltip says


  Capture a video of the active area or whole Blender window.


When I click it a circle appears over my mouse and an option to stop the capture appears on the right of the header.  When I click the button everything goes back to normal and nothing happens.

So what does this button do?  If it really made a video of what I did where did it save it?
The Make Screencast button allows you to save all actions you make in the Blender window to a video file.

From the doc:


  Screencasts will record your actions over time either as a video or sequence of image files. The type and location of the output is determined by the settings in the Output panel of the Render context window.


So the screencast video is saved to wherever you set under the Render tab > Output rollout.  It will also use whatever settings you set there for video output format as well.