Chemistry- Bonds( 10 Points Given)?

I'm having some trouble in chemistry because of bonds. It's not part of my homework but I just need to understand what Covalent Bonds, Nonpolar Covalent Bonds, Multiple Covalent Bonds, Double Covalent Bonds, Triple Covalent Bonds and Polar Covalent Bonds are. Or you can just say what's a covalent bond. I really appreciate it guys.