Blockchain

Peer-to-peer, distributed ledger comprised of a continuous chain of blocks, where each block builds upon the block before it.

Each new block added to the blockchain ledger builds upon the block before it, which built upon the block before that, which..., all the way back to the first genesis block. This innovation is one of many which are central to how bitcoin functions and allows anyone to independently verify the accuracy of the state of the blockchain ledger.