Merkle tree, also known as Hash tree, is a data structure that securely and efficiently encrypts large amounts of data. It is represented as a tree of hashes, in which every leaf node is labelled with the cryptographic 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 are a generalization of hash lists and hash chains and allow for verifications of large amounts of data. They provide secure and efficient verification of large amounts of data.