A simple definition
Blockchain is a way to record information in chronologically linked blocks. Each block contains data and a cryptographic reference to the previous block, helping preserve a verifiable history of the record.
Why is it called a distributed network?
In many blockchains, multiple computers keep copies of the same ledger and follow shared rules to validate new entries. This reduces dependence on a single central database.
Blocks, nodes and consensus
Nodes participate in the network, while the consensus mechanism defines how a valid state is accepted. Models include proof of work and proof of stake, each with different technical characteristics.
Blockchain is not the same as Bitcoin
Bitcoin uses a blockchain, but blockchain is a broader concept. Other networks use similar structures to run smart contracts, represent assets or record information.