Mesons are subatomic particles made up of one quark and one antiquark, which are types of fundamental particles. They are part of the hadron family, which also includes baryons like protons and neutrons. Mesons are typically unstable and exist for a very short time before decaying into other particles. These particles play a crucial role in mediating the strong force that holds atomic nuclei together. Mesons come in various types, such as pions and kaons, each with different properties and masses. Their study helps physicists understand the fundamental forces and interactions in the universe.