HDR (High Dynamic Range) essentially takes three images at different exposures and merges them together. The outcome produces darker dark areas and lighter light areas to produce much greater detail in an image in most cases. But some cases where lighting conditions aren't great it'll help to balance it out.
It's best used for landscapes or settings where lighting conditions are at non optimal angles like if a light is shining in your face or if the image your taking a photo of has light coming from behind causing the object in front to be shadowed. HDR will even it out to get a better image. Auto HDR will access the image and decide whether or not it's needed, if you leave HDR on all the time you may end up with some blurry images if it's not the right condition (moving objects) but if you want to make sure HDR is one during a time as mentioned above then turn it on so it's a sure thing. Hope that helps😊
