IR Illuminators are a form of special lighting that provide illumination in total darkness. The IR itself is invisible to the human eye but not for an IR sensitive camera. The camera is always in black and white or what those in the CCTV industry call mono mode. Mono is crucial to enable it to work. An IR illuminator will not work with a colour camera.
There are many high performance IR Illuminators on the market but Raytec and Clarius are the current market leaders. However there are a large number of cheaper options on the market.