Unlike a wide or narrow angle lens, a varifocal lens is a camera lens that can be adjusted to provide either a wide or narrow field of view. Varifocal lenses have more versatility than other types of lenses as they can be adjusted for the environment they are in, making them suitable for open spaces like parking lots and tight areas like hallways or alleys.
They are often found in standard dome cameras which are the most widely used type of dome camera.