Halogen bulbs are incandescent bulbs, just like the typical 60-watt A19 bulbs we have been used to for years and years. Halogen bulbs, however, are filled with a special gas that actually rebuilds the filament and provides longer average lifespans than normal incandescent bulbs. They come in different shapes and sizes for various different uses. The PAR20 series of halogen bulbs are flood shaped with the heavy, thick glass that is common to many medium to large sized halogen bulbs. PAR stands for parabolic aluminized reflector. These types of bulbs will provide you with a high light output, a more white-colored light (a higher color temperature - approximately 3000K), and longer life than normal R or BR reflectors.
The PAR20 bulbs are not as large as many halogen flood bulbs available. You can tell what kind of PAR lamp you have by measuring the distance across the widest point of the bulb. The number after 'PAR' represents the number of eighths of an inch the bulb diameter is. Therefore, PAR20 lamps are 2 1/2 inches across.
PAR20 lamps are widely available from Sylvania, GE, Philips, Westinghouse, and most other small bulb manufacturers. They have standard bases and are able to be used indoors or outdoors. This means they can be directly exposed to rain or snow and still function normally and they do not need to be covered by a light fixture. This makes the PAR20 lamps very versatile and quite handy to use.
The Sylvania brand for all PAR lamps is Capsylite. Philips brand for all PAR lamps is Halogena. The GE brand for all PAR lamps is Edison. The Westinghouse line uses only PAR to describe these bulbs. You can get the bulb in NSP (narrow spot), NFL (narrow flood), and WFL (wide flood) beam spreads. The NSP is about 10 degrees, the NFL is about 30 degrees, and the WFL is about 40 degrees. If you want to light up a large area, then use the NFL or WFL. If you want to focus the light into a small area, try the NSP. You can get all of these options in either 35 watt or 50 watt versions.
People use PAR20 lamps a lot in track lighting. From your local coffee shop to the Italian restaurant down the street, you will most likely find a PAR20 lamp lighting your way. Many people also use these halogen PAR20 bulbs for showcasing in home or office decor. The trophies, jewelry, art work, sculptures, etc. shown under this light will appear more brilliant and will display a truer color. Other places they are used are in smaller track lighting, floor lamps, and table lamps.