Merkle Tree

A tree structure in cryptography, in which every leaf node is labelled with the hash of a data block and every non-leaf node is labelled with the cryptographic hash of the labels of its child nodes. Hash trees allow efficient and secure verification of the contents of blockchains, as each change propagates upwards so verification can be done by simply looking at the top hash.

Sources:

https://coinmarketcap.com/alexandria/glossary/merkle-tree