Many-body localization is a state of interacting quantum matter characterized by a breakdown of thermalization and ergodicity in closed systems. It represents a distinct phase where quenched disorder prevents the system from acting as its own heat bath. This academic concept investigates the conditions under which interactions, combined with disorder, lead to the persistence of local information, logarithmic entanglement growth, and the absence of transport. Its significance lies in challenging fundamental assumptions of statistical mechanics regarding thermal equilibrium and providing a framework for understanding non-equilibrium quantum dynamics and potential applications in quantum information science.