The document discusses the basic structure of atoms. It describes the three main parts of an atom as the proton, neutron, and electron. It provides details on the location and composition of each part, including that protons and neutrons are found in the nucleus, electrons surround the nucleus, and protons and neutrons are composed of quarks. The document also defines related atomic concepts such as isotopes, the nucleus, and the electron cloud model which depicts the probability of finding electrons in different regions around the nucleus.