What Is Graphic Switching & Are There Reasons to Turn It Off?
Graphics switching is where the integrated graphics is switched for the discrete graphics when more performance is required (and where performance is more important than battery life &amp; heat output).

You can see the current graphics card that is enabled, and forcefully switch between the two, with gfxCardStatus.




Integrated graphics should be used when you need battery life over performance (the Integrated Only option in gfxCardStatus can be used to force integrated graphics in circumstances where OS X believes that the discrete graphics is required).
Discrete graphics should be used when you need performance over battery life (this is usually not required to be set manually with the Discrete Only option since OS X is happy to switch automatically).
Dynamic Switching uses the default OS X graphics switching.


When 'Automatic graphics switching' is disabled in the Energy Saver system preference pane, only the discrete graphics is used.