Lux is the unit of illuminance and luminous emittance, which measures luminous flux per unit area. In camera terms, this refers to how much light is required for you to be able to see. The lower the Lux level the better your image will be in dark or poorly lit conditions. With higher quality, DSP and sensor combinations resulting in lower Lux requirements will literally allow your camera to see in the dark!
Most MaxxOne cameras are able to see down to 0.01lux without infra-red lighting. But when used in conjunction with infra-red lighting produces amazing night vision without loss of quality.