Blockchain
Computational thinking, problem-solving and programming[1]
A block chain is a growing list of records, called blocks, that are linked using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree).[2]
A blockchain is a decentralized, distributed, and oftentimes public, digital ledger that is used to record transactions across many computers so that any involved record cannot be altered retroactively, without the alteration of all subsequent blocks[3]
Videos[edit]
The video below is easily the best video explanation I have found explaining blockchain. I would suggest you watch it several times.
The video below is a very good high-level overview of blockchain: