The blockchain technology derives its name from its functionality. It’s a timestamped and hash-linked ledger of transactions distributed across a computer network to guarantee immutability. Transactions recorded on it are bundled together into groups referred to as blocks based on some pre-set specifications like block size and confirmation times, then chained to the finalized or validated block prior. Bitcoin, for example, has a block size of 1MB and a confirmation time of 10 minutes.
It’s also referred to as a decentralized ledger technology as the ledgers are duplicated across all of the computers, referred to as nodes on the network, with a strict condition that requires all nodes on the network to come to an agreement or consensus before any individual ledger or database is updated and broadcasted across the network.
The more independent computers on a blockchain network, the more decentralised and secure it is. For some networks like Bitcoin which uses Proof of Work (PoW), to keep the time required for transactions in a block to be irrevocable steady as the network grows, reaching consensus is made more difficult.