Didn't know what it was, in fact. Also see you can set the phone to keep the 'normal' shot.

While getting some info I stumbled on this iphone tutorial that explains HDR well and demonstrates the built-in as well as a Pro HDR app. for most smart phones. Sometimes a phone is the only camera at hand so this is good info for me.

http://iphonephotographyschool.com/hdr/