A meson is a type of subatomic particle made up of one quark and one antiquark, which are fundamental constituents of matter. Mesons are part of the hadron family, which also includes baryons like protons and neutrons. They are typically unstable and exist for very short periods before decaying into other particles. Mesons play a crucial role in mediating the strong force that holds atomic nuclei together. This force is essential for the stability of matter, and mesons are often involved in interactions between nucleons, which are the protons and neutrons in an atomic nucleus.