What Role Does “Merkle Root” Play in Verifying the Integrity of All Transactions within a Bitcoin Block?

The Merkle Root is a single hash contained in the block header that is the result of repeatedly hashing pairs of transaction hashes until only one remains. It acts as a digital fingerprint for all transactions in the block.

By verifying the Merkle Root, a light client can efficiently confirm that a specific transaction was included in the block without downloading the entire transaction list, which is vital for Scalable Payment Verification (SPV).