B-meson mixing refers to the phenomenon where a B-meson, which is a type of subatomic particle made up of a bottom quark and a lighter quark, can oscillate between its matter and antimatter states. This means that a B^0 meson can transform into its antiparticle, the B^0-bar, and vice versa. This mixing occurs due to the weak force, one of the four fundamental forces in nature. The study of B-meson mixing is important in particle physics because it provides insights into the behavior of quarks and helps scientists understand CP violation, which is the difference in behavior between matter and antimatter. Observing these mixing patterns can also shed light on the Standard Model of particle physics and potential new physics beyond it.