Down quarks are elementary particles that are one of the six types of quarks. They have a negative charge and are found in the nucleus of atoms.
Up Quarks: Up quarks are another type of elementary particle that have a positive charge and also reside in the nucleus of atoms.
Protons are composite particles made up of two up quarks and one down quark. They carry a positive charge and contribute to the overall mass of an atom.
Neutrons consist of two down quarks and one up quark. They have no net electric charge but contribute to the mass of an atom.