Point Defense Lasers are weapons found on Covenant ships. They are mainly used to shoot incoming Archer missiles. According to John-117 they were "Too damn accurate..."[1].
Not much else is known about the Point Defense Laser, but that the Covenant must have adapted the technology from the Forerunners and that the Laser is like 'the Sniper Rifle of space battles'. The technology used is likely similar to the Particle Beam Rifle found in Halo 2 and 3, only scaled up with the capability to destroy Archer missiles and anything else smaller that comes within it's range.
References
- ^ The Fall of Reach page 122