Minecraft added an FPS throttle for when you are AFK (idling for too long) or when the window focus is lost. While this in essence is a good thing, this can lend itself to some odd consequences when developing, making content, or otherwise enjoying the game running smoothly. Thus the third option was added which allows you to disable the throttle all together and be classified as always "at your keyboard".
Note: This is currently only toggleable through the modded config. More granularity may come in the future.
The No Frame Limiter Team
