Ellipsoidal lights are the backbone of theatrical productions. This kind of stage lighting falls under the broader category of focusing lights. They are equipped with shutters that allow lighting technicians to obstruct part of the ray of light sent forth. This allows for an area of the stage to be partially lit, as well as for the intensity to be softened or made harsher.
Another very common theatrical light is the fresnel. The biggest advantage of the fresnel light is that the thickness of the lens is reduced, which not only increases the transmission of light, but also reduces the potential for the glass fracturing due to heat. A fresnel spotlight is often used to soften the light in order to create a luminescent effect.
In theatrical lighting terms, a flood light is referred to as a "scoop." A scoop is shaped like a metal helmet and typically houses a lamp with high wattage. Because there is little control over a scoop, it is rarely used during performance. The most effective use of a scoop light is to provide a broad flood of light, since just a few of them can light a substantial area of the stage.
Strip lights are often called cyclorama lights. Typically, strip lights consist of a row of lamps. To achieve certain mood lighting effects, technicians will often place a colored sheet of plastic known as a gel over a the individual lamps inside a strip light. Computer advances have made it possible for a lighting director to control each individual row of lights with a dimmer to create even more sophisticated effects.
PAR stands for parabolic aluminized reflector lights. These lights are lightweight and easy to use, and can send a quite voluminous amount of light to the stage. Many people may have seen PAR lights in action not just on the stage, but in their use as a source of illumination in larger architectural structures like warehouse stores. Because of their low cost and durability, PAR lights are also often found at music concerts.
"Spotlights" is a general term used to describe any stage light that is capable of creating a pool of light that can be moved easily. Spotlights also have the ability to expand and contract the beam of light from a much broader pool of light to a pinpoint that can illuminate just the face of a person on stage.