An antiquark is a fundamental particle that is the counterpart to a quark. While quarks are building blocks of protons and neutrons, antiquarks have opposite properties, such as charge. For example, if a quark has a positive charge, its corresponding antiquark will have a negative charge. Antiquarks combine with quarks to form mesons, which are particles made of one quark and one antiquark. Antiquarks are part of the Standard Model of particle physics, which describes the fundamental particles and forces in the universe. They play a crucial role in understanding strong interactions, the force that holds atomic nuclei together, and contribute to the study of antimatter, which consists of particles that have opposite charges and quantum numbers compared to their matter counterparts.