Definitions

CCT: Correlated Color Temperature.  Corresponds to apparent color of a black body heated to that temperature in degrees Kevin.  The higher CCT, the light appears more bluish.  Lower CCT (< 3000K) correspond to "warm white" similar to incandescent lamps.  The sun's CCT is 6500K, but due to variable reflection and absorption of molecules in our atmosphere, sun light color varies with time-of-day.

CRI: Color Rendering Index.  By definition CRI of a radiating black body is 100.  Incandescent lamps usually have CRI of 100 unless their enclosure or reflector is deteriorated.

Glare: We want to see objects around us, not the lights coming from light sources that illuminate the objects.  Direct light from light sources into our eyes reduces our view of objects and is called glare.  Recessed lights ideally have no glare when properly designed.  However recessed lights fitted with compact fluorescent lamps can be seen from far away, thus are not glare-free.  LED spot lights are mostly glare-free.  Pictures taken in a room with glare-free lighting will show people more clearly, as opposed to very bright spots and dark people when glaring lamps are used.

Luminous Efficacy: how many lumens you get for each watt of input power.  Incandescent bulbs provide about 10 lm/W.  Newer LED bulbs provide in excess of 50 lm/W.

Luminous Flux: measured in lumens, is the total amount of light the luminaire puts out, after inevitable losses in the electronics and optics.

Power Factor:  The ideal power factor of an appliance is 1, such as found among simple incandescent light bulbs or your toaster oven.  Electronic power supplies for LED lamps typically boast a lower power factor due to the need to convert the household AC power into a regulated DC (direct current).  A lower power factor, such as 0.5, means the current going into the appliance is twice the ideal case.  Thus a higher power factor is recommended.  DoE mandates PF > 0.7 for residential bulbs and PF > 0.9 for commercial lamps.

Apparent Power:  the input current to an electric appliance such as a refrigerator is not always in phase with the mains voltage, nor sinusoidal in most cases.  The product of the mains voltage and the input current is called the apparent power, which is most of the times higher than the real power consumed by the appliance to perform useful work such as pumping fluid or run a motor.