What are the differences between ionic, polar covalent, nonpolar covalent, and hydrogen bonds?

Whereas non-polar bonding involves the equal sharing of electrons between identical non-metal atoms, polar bonding is the unequal sharing of electrons between two different non metal atoms. A proper understanding of polar bonding is gained by viewing the types of bonding on a continuum. Ionic bonding is on one extreme with a complete transfer of electrons forming charged ions. Non-polar covalent bonding with equal sharing of electrons is at the other extreme. Somewhere in the middle but favoring the covalent side is polar bonding with unequal sharing of electrons and partial but incomplete transfer of electrons.