LED Terminology

Coloring Rendering Index (CRI) - CRI represents the quality of light and its faithfulness to render colors correctly, that is, to enable us to perceive colors as we know them. The ideal CRI is 100, and some incandescent bulbs approach this level. LEDs and CFLs use different design components in trying to equal the CRI of incandescent bulbs. LED bulbs CRI ratings range from 70 to 95, and the best CFLs have ratings in the mid 80s. The LED CREE CR6 bulb, for example, features a CRI of 90 Warm White making it one of the highest in the industry.

Correlated Color Temperature (CCT) - is the measure used to describe the relative color appearance of a white light source. CCT indicates whether a light source appears more yellow/gold/orange or more blue, in terms of the range of available shades of "white." CCT is given in kelvins (unit of absolute temperature). 2700K is "Warm" and 5000K is "Cool". The typical light color we are used to in indoor home lighting is "warm", 2700 - 2800K.

Lumen - a unit of standard measurement that is used to describe the amount of light contained in an area as perceived by the human eye. The more lumens, the brighter the light. You can use lumens to compare the brightness of any bulb, regardless of the technology behind it, and regardless of whether it's incandescent, CFL or LED. 

Luminous Flux - the flow of light measured in lumens. With light bulbs, it provides an estimate of the apparent amount of light the bulb will produce. Depending on the application, much of an incandescent's light is wasted because it's emitted in every direction. LED bulbs, on the other hand, put out directional light, sending all of the light exactly where it's needed. 

In practical application, when buying a light bulb, we should look for bhlbs which produce more light but consumes less energy. Understanding lumens as a measure of brightness makes it easier to select the most efficient bulb for your application. This is also important