By default, your iPad is set to automatically change its display brightness, thanks to a built-in light sensor, depending on ambient light - note that this has nothing to do with the automatic dimming of the screen that occurs when the iPad is trying to save some battery after a few moments of inactivity. While this option is often practical, and typically makes your battery last longer on a charge, it can also be quite distracting, which is why Apple lets you disable this Auto-Brightness and prevent your iPad from automatically changing the screen's brightness, as you'll learn in this tutorial.
Follow these steps to disable this feature:
Tip: if you decide that you want to re-enable the Auto-Brightness option later on, just follow the steps outlined above, but this time set the switch to "ON".
Tip # 2, concerning the inactivity auto dimming of the screen: as mentioned earlier, your iPad will try to conserve battery life by automatically dimming the screen (make it less bright) after a certain period of inactivity - just tap anywhere on screen to bring the display back to its normal brightness. If you have a keyboard plugged into your iPad, just hit a neutral key (like Control), and the screen will "wake up".