Quantum numbers are a set of numerical values that describe the unique quantum state of an electron in an atom. They provide information about the electron's energy level, shape of its orbital, orientation in space, and its spin. There are four main quantum numbers: the principal quantum number (n), the azimuthal quantum number (l), the magnetic quantum number (m_l), and the spin quantum number (m_s). Each quantum number has specific rules and ranges. The principal quantum number (n) indicates the energy level, while the azimuthal quantum number (l) defines the shape of the orbital (like spherical or dumbbell). The magnetic quantum number (m_l) specifies the orientation of the orbital, and the spin quantum number (m_s) describes the electron's intrinsic spin, which can be either +1/2 or -1/2.