Thin films and multilayers have applications in the development of sensors, neutron guides and beam deflectors. Adsorption of surfactants and polymers is important in technological and industrial applications, and characterization of these thin films is essential for their use in appliances. The special features of neutron interaction with matter make neutron reflectometry a powerful tool for probing these surfaces and multilayers. It is also useful in surface studies of corrosion of metals. The additional advantage of the method is that it can also be effectively used with medium flux reactors. This publication gives an introduction into the theory underlying this method, its potential applications and a description of existing facilities. It will be useful as a guide to the neutron beam user groups interested in developing a neutron reflectometer and enhance reactor utilization.