What is Auto Deleveraging (ADL)?

[Bitcoin_Arena]

Even since I started trading futures over a year ago, I have failed to understand what Auto Deleveraging (ADL) means. I have read a few blogs but can't quite understand what they are exactly trying to mean maybe because of the terminology used.

Can someone with experience and a much better understanding help me understand what ADL means in a layman language if possible?
Of what significance is it to a trader with an open position?