Lux, (Latin for light) is a unit of measurement used to quantify the level of illuminance or the amount of light that falls on a surface. Specifically, it measures the intensity of light in lumens per square meter.

In simple terms, Lux indicated how bright a surface is when illuminated by a light source. The higher the lux value, the brighter the surface will appear.

A comparable example:

A unit that in this case is more universal, is Candela. Candela is the general unit of measurement in order to calculate light.