A "boom" mic is a supercardioid mic that is pointed at the subject from a distance--and thus invisible to the viewer.

A fishpole version is attached to a stick; a studio boom attached to a much larger apparatus (and used only in a studio) but the idea is basically the same.

Because these mics are slightly off-camera, they work well for dramatic productions because they cannot be seen. Booms can gather very high quality sound, and they free up actors from having to worry about mic cables and wires.

One significant issue is that a crew person is needed to hold these mics. In contrast,, a lav mic can be clipped on before shooting; but a boom must be "pointed" by somebody during the shot.