PAR stands for “Parabolic aluminized reflector.” The number after the PAR indicates the diameter of the bulbs which differentiates each PAR type. To find the diameter, multiply the PAR number by 1/8.
PAR bulbs have a lamp, reflector, and pressed lens inside the lamp to give directional lighting. PAR bulbs have a narrow beam angle and spread light at 45 degrees or lower. They have soft light which can lead to shadows.
PAR bulbs are normally found in places like theaters, retail displays and even exterior landscaping.
A PAR 38 bulb is a type of PAR bulb usually used for outdoor lighting. These bulbs can cover larger distances because they have a higher wattage. They can be used as general flood and safety lights as well. A benefit of using PAR 38 bulbs is that they have adjustable beam angles and dimming capabilities. This allows you to adjust the lighting to your own preferences. The diameter of the PAR 38 bulb (38 * 1/8) is 4.75 inches.