What is selectivity in glass?

Selectivity is the optical property of glass (or other materials) which allow to pass a large part of visible light, but reflects or absorbs a large part of non-visible light (such as ultraviolet and infrared).

This is a good feature for buildings since, sometimes, we want more daylight to go through the Windows but we do not want heat to get in the building. It is important to mention that ultraviolet and infrared light (or energy) carries heat but not illumination (or visible light).