Hadronic matter refers to ordinary matter composed of hadrons, which are subatomic particles that interact via the strong force, primarily protons and neutrons. These particles form the nucleus of atoms and account for most of the mass of ordinary matter, with electrons contributing minimally. The significance of hadronic matter in cosmology lies in its limitations; it cannot fully explain the gravitational effects observed in galaxies, leading to the inference of dark matter, which is believed to account for the missing gravitational mass. The discussion also touches on the classification of particles, including leptons, mesons, baryons, fermions, and bosons, highlighting the diverse nature of matter in the universe.