A hydrogen bond is a type of weak chemical bond that occurs when a hydrogen atom, which is covalently bonded to an electronegative atom like oxygen or nitrogen, experiences an attraction to another electronegative atom. This interaction is crucial in many biological and chemical processes, as it helps to stabilize the structures of molecules such as water and DNA. Hydrogen bonds are generally weaker than covalent bonds but stronger than van der Waals forces. They play a significant role in determining the properties of substances, including water's high boiling point and the unique structure of proteins. Understanding hydrogen bonds is essential in fields like chemistry, biology, and materials science.