A headlamp is an illuminating device that is worn on a person’s head and an LED is “a semiconductor diode that emits light when a voltage is applied to it and that is used especially in electronic devices (Merriam Webster’s definition). Together these two form what we know to be an LED headlamp. The LEDs used in these headlamps do vary from the commonly seen LEDs that are used on various electronic devices. The LEDs produce far more light which is required for activities done commonly in the outdoors and in particular low visibility, low light and dark conditions. The LEDs used also consume less power so even if they are very bright the runtime for these headlamps is very much extended. The runtime and brightness though varies from flashlight to flashlight but generally you can expect a bright light that lasts longer than the average flashlight because of their low power consumption.
It is also worth mentioning that the evolution and popularity of these headlamps have originated from industry and now also strongly represent the recreational market as well. Their hands-free use makes them very popular and a preferred light source for many who need the use of both their hands in doing their work or recreation of choice.
When looking for an LED headlamp, make sure the light is bright enough for the particular task it is required to fulfill. Consider the runtime as well, you might be working in a mine or caving for recreation and have appropriate lighting but the lights might go out pretty quickly and you don’t want to be down that dark place with the lights out. Make sure as well that it fits your head just right.