What Is the Role of the ‘Merkle Root’ in Linking the Transactions in a Block?

The Merkle Root, or transaction root, is a single cryptographic hash that summarizes all the transactions included in a block. It is calculated by repeatedly hashing pairs of transaction hashes until only one root hash remains.

This root is stored in the block header. Its primary role is to allow for efficient and secure verification that a specific transaction was indeed included in the block without needing to download all transactions.