How does a polar covalent bond differ from a nonpolar covalent bond?

In a nonpolar covalent bond, atoms share electrons equally. So whenever you have 2 of the same kind of atom, they're going to share electrons equally because they have equal electronegativities.

A polar covalent bond is a chemical bond where a pair of electrons in the energy levels of a certain kind of atom are not equally distributed or shared shared between two atoms.