The phrase "hinge system" refers to a mechanism that allows two things to pivot or rotate around a fixed point. It is commonly used to connect and enable the movement of doors, gates, or lids. Full definition
The unique feature about this Kindle cover as compared to other Kindle covers is that it has a patent - pending hinge system which physically secures the device to its cover, plus there is a strap to help keep the cover firmly closed when it is put away after use. (ebookreaderguide.com)
To sum things up, you have a beautiful laptop with a strong hinge system for tablet use with a decent display. (androidcentral.com)
Amazon's patent - pending hinge system secures Kindle in place and conducts electricity from Kindle's battery to the reading light, eliminating the need for batteries. (reviewhorizon.com)