The term 'Proton Sites' refers to the NUCLEI of atoms, which are composed of protons and neutrons. Protons are positively charged particles that are found in the nucleus of an atom, while neutrons are neutral particles that also make up the nucleus. The number of protons in an atom's nucleus determines its atomic number, which is used to identify different elements. Therefore, the term 'Proton Sites' can be used to refer to the NUCLEI of atoms, which are composed of protons and neutrons.