Confocal microscopy refers to the technique of focusing the excitation light into parts of the focal plane and then focusing the returning emission through precisely positioned apertures which physically reject light coming from out of focus regions of the sample.

The area(s) in which the light is focused is rapidly moved across the sample to form the full image.

Lasers are used  in order to produce the highly focused light necessary for this family of techniques.

These last two points mean that confocal microscopes are most commonly referred to as Laser Scanning Microscopes (LSMs).

A number of different varations of confocal microsopy are available.