What does GOBO stand for? 

Gobo

A gobo derived from "Go Between" or "Goes Before Optics" is a physical template slotted inside, or placed in front of, a lighting source, used to control the shape of emitted light. In the design of an artificial environment in which lighting instruments are used, it is sometimes desirable to manipulate the shape of the light which is cast over a space or object. To do so, a piece of metal with patterned holes through which light passes is placed in the beam of light to allow only the desired "shape" or pattern through, while blocking the rest of the light, casting a specific shadow/light into the space. Though the term "gobo" has come to generally refer to any device which produces patterns of light and shadow or various pieces of equipment that go before a light, the specific term itself also defines the device used in theatrical lighting applications because of the mandated placement of the device in 'the gate' or 'point of focus' between the light source and the lenses. This placement is important because it allows the focusing of the pattern or shape into a crisp, sharp edge and also the softening the edges. Gobos placed in the beam of light post-optics do not have the option of such fine focus, and are more precisely called "flags" or "cookies."

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