What are Quantum Numbers?

The principal quantum number $n = 1, 2, 3, \dots$ gives the shell and its size. The azimuthal number $l = 0$ to $n-1$ gives the subshell shape ($s$, $p$, $d$, $f$ for $l = 0, 1, 2, 3$). The magnetic number $m_l$ runs from $-l$ to $+l$ and gives the orbital. The spin number $m_s$ is $\pm\tfrac{1}{2}$.