What is the Halo protection system to be used in Formula 1?

FIA, Formula One's governing body, has confirmed the use of a Halo cockpit protection system in cars from 2018 onwards. The Halo has been designed to reduce injuries from debris or other objects striking a driver's head. FIA also tested the 'Shield', a transparent open canopy system, but opted for the Halo since it had the "best overall safety performance".