What is a Merkle Tree?

A Merkle Tree is a structure that ensures data stays intact and unchanged by pairing the data with hashes of that data. A hash is a short fixed-length fingerprint computed directly from a piece of data — if any part of the data changes, the hash changes too. By combining data and hashes of that data together in this structure, it becomes possible to detect whether anything has been tampered with. For a beginner, the practical takeaway is that a Merkle Tree gives a system a reliable way to confirm that the data it holds is exactly the same data that was originally stored — nothing added, removed, or altered.