What's the difference between a bayron and a meson?

A baryon is a particle that is made up of three quarks (which are fundamental particles) bound by the strong force. A meson, on the other hand, is a particle which is made up of one quark and one antiquark. Because they are made up of a particle and an antiparticle, these systems are inherently more unstable than their baryonic cousins as the antiquark-quark pair are likely to annihilate each other!