Some electric lighting is necessary for every interior space. Proper light source selection depends on the functional and aesthetic requirements placed on the lighting system, economic and energy usage restrictions, and the personal preferences of the designer and/or the owner of the space. Each lighting technology has unique characteristics that make it more or less desirable for specific applications. In this document, details are provided regarding operating principles, characteristics of the technology, and configuration of systems. The intent is to help facilitate light source selection for those involved in the design of the luminous environment, including architects, interior designers, engineers, lighting designers, owners, sustainability consultants, energy engineers, landscape architects, lighting product representatives, lighting manufacturers, contractors, and distributors.