as a covalent bond is a bond between atoms sharing electrons, a polar covalent bond is a covalent bond where the difference in electronegativity of the two atoms is uneven (one is greater than the other). This meaning that one atom will have a greater pull on the electrons towards them than the other and the share of electrons is uneven (definition of polar). A non polar covalent bond is one where the difference in E.N is small or non existent and the balance of shared electrons is even
