A tutorial overview is given on interactions between atoms and surfaces that are mediated by the electromagnetic field. The emphasis is on dispersion (or van der Waals) forces and transitions induced by thermal fluctuations in the near field of a surface. Applications with cold atoms held in microscopic traps near surfaces ("atom chips") provide the experimental background for this theory lecture. We do not cover the chemical physics aspects that are relevant at distances comparable to the atomic scale, like adsorption and diffusion on surfaces, growth of nanostructures, or atomic beam diffraction from crystalline surfaces. These are covered by other lecturers.