PAR Lights, otherwise known as 'Parabolic Aluminized Reflector' lights, are bulbs which use refraction to improve the light output. Or rather, this is how these type of bulbs used to work, before LEDs came into existence.
Their typically cone shape would allow light to bounce and bend off the interior, therefore increasing the brightness of the light.
However these days, LEDs are powerful enough to not require much in the way of assistance in order to provide a very bright light automatically.
Instead, PAR LED Bulbs tend to rely on multiple LED reflectors in order to direct the light appropriately. This allows the light to be directed outwards, just as a traditional PAR lamp is required to do.
Available in a screw cap fitting, these are available in varying diameter sizes. For example, a PAR20 bulb has a diameter which is 1/8 of an inch, multiplied by 30. This means a PAR20 bulb has a diameter of 2.5 inches.
LEDs continue to provide the highest levels of energy efficiency for any type of bulb, offering up to 50,000 hours of life per bulb. No other type of lamp currently comes close to competing with that level of lifespan; and so the fact they rarely require replacement is one of an LED bulb’s best selling points.
Additionally, these type of bulbs run cool, as they have no filament to heat up and use energy. This in turn makes them cheap to run, as well as infrequent to replace.