The properties of the atomic nucleus are summarized and shown to be consistent with a description in which the nucleus is regarded as an assembly of elementary particles (neutrons and protons) bound together by means of nuclear forces. Because of the formidable difficulty of giving a full theoretical treatment of this many- body problem, nuclear models are introduced which can account in a semi-quantitative fashion for many of the nuclear properties. Finally, a discussion is given of the way in which these models are related to one another and to a 'true' description of the nucleus.