- A powerful data structure to improve our protocol's scalability
- A hash of a hash of a hash of a hash... of all the data until there's just 1 hash - the "root" of the tree. A guy named Ralph Merkle invented this as a data structure.
Merkle Proof / Branch
- The set of hashes in a merkle tree necessary to verify that a piece of data is within the merkle tree. This allows you to verify the integrity of a piece of data within a data set by checking much less than the full set of data. This is what light clients on Ethereum or Bitcoin do.
Wikipedia: Merkle Tree - Wikipedia page on Merkle trees.
Brilliant: Merkle Tree - Free page explaining merkle trees.
Pegasys: Ethereum Explained - Explains Merkle trees in the context of Ethereum.