A Merkle Tree is a well-known method of structuring data that allows a large body of information to be verified for accuracy extremely quickly and efficiently. Every Merkle Tree results in a single alphanumeric code that acts as a digital fingerprint for the entire body of data.
The digital fingerprint is known as the Merkle Root.
For Bitcoin-protocol blockchains, a block’s Merkle Root results from the Merkle Tree of all of that block’s transaction IDs. The Merkle Root acts as a fingerprint for all of the block’s transactions.