The bond formed between a hydrogen on one polar molecule and a very electronegative atom like oxygen or nitrogen on another molecule is called a hydrogen bond.

Here's why:

* Polarity: The electronegativity difference between hydrogen and oxygen or nitrogen creates a polar bond, with the hydrogen atom carrying a partial positive charge (δ+) and the oxygen or nitrogen carrying a partial negative charge (δ-).

* Electrostatic Attraction: The partially positive hydrogen atom is attracted to the partially negative oxygen or nitrogen atom of a nearby molecule. This attraction forms the hydrogen bond.

Important Note: Hydrogen bonds are weaker than covalent bonds but are still significant in many biological and chemical processes.