A flashlight (in American English) or torch (in Commonwealth countries) is a small, portable spotlight. Its function is a beam of light which helps to see. It usually requires batteries.
The light is made by a small light bulb. In the 20th century, it was usually an incandescent bulb. Nowadays most use LEDs, which work slightly differently. In 1896, the first dry cell battery was invented. Unlike previous batteries, it used a paste electrolyte instead of a liquid. This was the first battery suitable for portable electrical devices, as it did not spill or break easily and worked in any orientation. Sometimes the electricity comes from a small generator instead of a battery.
The torch can also refer to a flammable stick that is lit on fire to provide light and (or) heat.