Here's a breakdown:

* Hydrogen Bonding: Hydrogen bonds are a type of weak chemical bond that forms between a hydrogen atom covalently linked to a highly electronegative atom (like oxygen or nitrogen) and an electron pair in the adjacent molecule.

* Base Pairing: In DNA and RNA, the nitrogenous bases form specific pairs:

* Adenine (A) pairs with Thymine (T) in DNA or Uracil (U) in RNA.

* Guanine (G) pairs with Cytosine (C).

* How it works: Each base has specific functional groups that allow for the formation of two or three hydrogen bonds with its complementary base.

* Importance: These hydrogen bonds are crucial for:

* Holding the two strands of DNA together.

* Ensuring the correct base pairing, which is essential for DNA replication and transcription.

* Maintaining the double helix structure of DNA.

Let me know if you'd like a visual representation of these bonds!