Many MacBook Pro models have two graphics systems — an integrated graphics processor and a discrete graphics processor — and a software feature that optimizes graphics performance between them.
On these computers, the 'automatic graphics switching' option is turned on by default to allow your computer to automatically switch to the best graphics system for the applications running on your computer. Using this option may also maximize battery life.
High Performance mode uses the nVidia 9600M GT dedicated graphics. Better Battery Life mode uses the integrated nVidia 9400M graphics. Not as powerful but better battery life. I tend to keep mine on High Performance just for convenience, but I'll switch to the 9400M if I know I won't need the powerful graphics and need the battery life.
When your computer is connected to an external display, high-performance graphics remain on until you disconnect the display.
If you want to use the higher-performance discrete graphics processor at all times, choose Apple menu > System Preferences and click Energy Saver. Then deselect the automatic graphics switching checkbox.
If you don't see the automatic graphics switching option, your computer has one graphics system. To confirm, choose Apple menu > About this Mac, press the System Report button, and select Graphics/Displays on the left. The graphics system or systems are listed under Video Card.
Learn more
Learn about setting the graphics performance on earlier MacBook Pro models and how to determine which graphics card is in use on a 15' or 17' MacBook Pro.