Blockchain
Distributed ledger storing transactions in a cryptographic chain of blocks.
Blockchain: distributed database held by thousands of nodes. Each block hashes the previous, falsifying history requires >50% network control. Consensus (PoW/PoS) picks block producer. No central admin.
In plain words
A transaction database whose copy is held by thousands of computers worldwide at once. Each new entry (block) is cryptographically signed and tied to the previous one. To rewrite history you'd need to break a majority: economically impossible on Bitcoin.
Example
Bitcoin: 880k+ blocks since 2009, one every ~10 min. Full history (600+ GB) synced across 20k+ nodes worldwide.
Also known as: łańcuch bloków, DLT, distributed ledger