A fixed lens camera is one that cannot be adjusted to zoom in and out and is normally used for indoors or monitoring closer areas. Fixed lens cameras are normally a cheaper choice and can save you some money if you don’t need to have a zoomed in view of an area.
A varifocal or vari lens camera has the ability to optically zoom in on an area. The variable focal length can be used to change from a wide-angle view covering a large area to a narrow focal view to centre on a particular area at a long or short range. This is a popular choice of self-installation as it is versatile and can easily be adjusted to suit your needs.