A fixed lens for security cameras means that the focal length of the lens is fixed and cannot be changed. This type of lens provides a constant angle of view, which is useful for situations where you need to monitor a specific area without changing the field of view. Fixed lens cameras are usually simpler and more affordable than varifocal cameras where the angle of view can be changed. They are ideal for use in environments where monitoring requirements are specific and constant, such as entrance doors, corridors or other confined spaces.