LED stands for Light Emitting Diode. These semiconductor diodes emit light when voltage is applied to them. They are used in a variety of applications such as electric lighting, flashlights, traffic lights, streetlights, and alphanumeric displays that appear on digital watches, calculators, and scoreboards, for example. They may also be used as a signal that power is on, and in this role appear on computers, appliances, and on garage door openers. An LED is placed in some kind of LED holder in many cases in order to easily and securely insert it into its working position.
When purchasing LEDs for a project, one will find that some LEDs come already attached to an LED holder, while some LED holders are offered for sale separately. LEDs already placed in an LED holder are often found in 4mm, 5 mm, and 6 mm (.157, .197, and .236 in), and colors such as orange, green, and red, as well as red/yellow. This type of LED holder should not be confused with an LED installation. They are small and inexpensive and often used as power indicators.
There is a much greater variety with the independently sold LED holder. First, there is a wide range of material. An LED holder may be made of thermoplastic, brass, painted plastic, chrome, or a combination of materials. Holders may be square or round, and they may screw into place or be of the snap-in variety. Holder colors are often black, white, chrome, or brass.
Some LED holders are specifically made for a particular application. Examples include replacement parts for a particular brand of CB radio, printer control panel, or computer. One can also find enhancements for automotive applications and generic holders, such as holders for a standard lamp socket. Although most LED holders are made to hold the LED when it is in use in an appliance or device of some kind, there is also a type of LED holder made for holding an LED light source when it is not being used. Many LED holders are sold on their own, but in some cases, an LED holder may be sold combined with a power switch.