A covalent bond is a chemical bond characterized by the sharing of electron pairs between atoms, typically occurring between non-metals or atoms with similar electronegativities. There are three types of covalent bonds based on shared electron pairs: single, double, and triple, along with polar and non-polar distinctions. Common elements forming covalent bonds include hydrogen, nitrogen, carbon, halogens, and oxygen, as exemplified by water, which has a polar covalent bond due to the differing electronegativities of hydrogen and oxygen.