Blockchain can be described as a sequential transaction database found in cryptocurrencies such as Bitcoin.
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A distributed hash table (DHT) is a class of a decentralized distributed system that provides a lookup service similar to a hash table. Any participating node can efficiently retrieve the value associated with a given key. wikipedia 
In cryptography and computer science, a hash tree or Merkle tree is a tree in which every non-leaf node is labelled with the hash of the labels of its children nodes. Hash trees are useful because they allow efficient and secure verification of the contents of large data structures. Hash trees are a generalization of hash lists and hash chains.