Final answer:
A nonpolar bond is formed when two atoms share electrons equally, while a polar covalent bond is formed when electrons are shared unequally.
Step-by-step explanation:
A nonpolar bond is formed when two atoms share electrons equally. This means that the electrons are shared in a symmetrical way, resulting in no partial charges on the atoms. In a polar covalent bond, on the other hand, the electrons are shared unequally, leading to partial charges on the atoms.