Landau levels are quantized energy levels that electrons occupy in a magnetic field. When a charged particle, like an electron, moves through a magnetic field, its motion becomes circular due to the Lorentz force. This results in discrete energy states, rather than a continuous range, which are known as Landau levels. These levels arise from the interaction between the magnetic field and the electron's motion, leading to unique physical phenomena. Quantum Hall effect is one such phenomenon that occurs in two-dimensional electron systems at low temperatures and strong magnetic fields, showcasing the significance of Landau levels in condensed matter physics.