As name refered, this filter reduce the reflection and allow the more light passing the filters to raise the transmittance (reducing reflection). Anti reflection filters were the first optical filter to be made by human. It was widely used in Binoculars, Glasses, Digital Camera, Cover glass of camera, Glass of LCD projection system, Optical cover glass, Optical Instruments and the products which need a high transmittance of the light.
Also named as AR for short.