Spotlights are often used in photography as a main source of light. A spotlight will shine a narrow, concentrated and crisp light beam that is generated by an undiffused clear flashtube. To direct and focus the spotlight, you can use a Fresnel lens or a small reflector with a mirror finish.
Spotlights are quite powerful and they can produce light that is similar to direct sunlight on a bright, clear day. The rays of light from a spotlight are basically parallel and aren't diffused in any way. Spotlights will cast crisp shadows that are hard and have sharply defined edges. These types of lights are generally used to highlight a certain feature of your subject or as a hair or background light and are often used in the studio and theatre. Spotlights are available in various colors sizes and powers.