The magnetic quantum number ml

The magnetic quantum number ml describes how the various orbitals are oriented in space. The value of ml depends on the value of l. The values allowed are integers from –l to 0 to +l. For example, if the value of l = 1 (p orbital), you can write three values for ml: –1, 0, and +1. This means that there are three different p subshells for a particular orbital. The subshells have the same energy but different orientations in space. Figure below shows how the p orbitals are oriented in space.

Notice that the three p orbitals correspond to ml values of –1, 0, and +1, oriented along the x, y, and z axes.