PAR lights are easy to identify. These lights are housed in a cylindrical can-shaped housing and have a flat, round lens that resembles a car headlight.
PAR lights shine an intense, focused oval of light at its target. Different sizes of lenses are available that change the diameter of the cone of light. The most common result is a beam with an 8-inch (or so) diameter.
Various filters may be applied to the PAR light to create colored beams. Newer LED PAR lights create colors without needing filters.
PAR lights are great for lighting from above and are best used in rows to light an entire stage or to provide a wash of color. They are rarely used as house lights because they cannot be focused.
A raylight reflector may be added to a PAR light to create a more intense and focused beam of light. Useful during concerts, it helps the light be seen better.