A polar bond is formed when two elements come together to form a compound and the two elements have different electronegativities (EN). For example, the EN of H is 2.1 and Cl is 3.0, the difference is 0.9. For a 50% ionic/covalent character, the difference is about 1.8 or so. A 100% covalent/0% ionic character has a difference of zero. Thus the 0.9 HCl is a polar covalent bond. It is not pure covalent and it isn't pure ionic but in between.
