A gobo or gobos are a piece of flat steel or glass, which when placed in a lighting fixture projects the image that is on the gobo. The image can be a solid color, pattern, shape, design or even your monogram or name.
The word gobo is an acronym for the phrase “Goes Before Optics.” There are specific lighting instruments that can accept gobos. The most common is an ellipsoidal, which are lighting instruments that allow you to focus the light and gobo by moving the lens back and forth in the lens tube. Focus ensures that your monogram will be crisp and sharp.