The principal quantum number (n) describes the size of the orbital.
The angular quantum number (l) describes the shape of the orbital.
The magnetic quantum number (m) describes the orientation in space of a particular orbital.
Orbitals have shapes that are best described as spherical (l = 0), polar (l = 1), or cloverleaf (l = 2). They can even take on more complex shapes as the value of the angular quantum number becomes larger.
(n) cannot be zero. The allowed values of n are therefore 1, 2, 3, 4, and so on
(l) can be any integer between 0 and n - 1. If n = 3, for example, l can be either 0, 1, or 2.
(m) can be any integer between -l and +l. If l = 2, m can be either -2, -1, 0, +1, or +2.