What Is the Role of the Merkle Root in a Block Header?

The Merkle Root, also known as the root hash, is a single hash value included in the block header that summarizes all the transactions within that block. It is the top node of a Merkle Tree, a data structure where pairs of hashes are repeatedly hashed together until only one remains.

The Merkle Root allows for the quick and efficient verification that a specific transaction was included in the block without having to download and process every single transaction.