A blockchain is a distributed ledger with growing lists of records (blocks) that are securely linked together via cryptographic hashes.Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree, where data nodes are represented by leaves). The timestamp proves that the transaction data existed when the block was created. Since each block contains information about the previous block, they effectively form a chain (compare linked list data structure), with each additional block linking to the ones before it. Consequently, blockchain transactions are irreversible in that, once they are recorded, the data in any given block cannot be altered retroactively without altering all subsequent blocks.
What is blockchain technology?
A decentralized, distributed ledger that securely and openly records transactions is defined.

Blockchain technology was first introduced with the launch of Bitcoin in 2008 and has since grown to be used in a wide range of applications.

Technical details: Blockchain secures and verifies transactions using cryptography and hashing, and validates them using consensus techniques.

Applications: In addition to cryptocurrencies, blockchain has been utilized in supply chain management, voting systems, smart contracts, and other areas.

Limitations: Blockchain is criticized for using a lot of energy and for having problems scaling.