Here's why:

* Polarity: Hydrogen bonds form between molecules where one atom has a significantly higher electronegativity than the other. This creates a partial positive charge on the hydrogen atom and a partial negative charge on the other atom (usually oxygen, nitrogen, or fluorine).

* Attraction: The partially positive hydrogen atom is attracted to the partially negative atom of a neighboring molecule. This creates a weak electrostatic attraction.

* Weakness: While hydrogen bonds are stronger than van der Waals forces, they are still much weaker than covalent or ionic bonds.

Examples:

* Water molecules form hydrogen bonds with each other, giving water its unique properties like high boiling point and surface tension.

* DNA strands are held together by hydrogen bonds between the base pairs.

Let me know if you would like more information on hydrogen bonds or other types of intermolecular forces!