Think of blockchain as a database or a spreadsheet. But a really special spreadsheet. There's no centralized master copy. Instead, it's shared on many computers. It's special because you can only add to it. There's no editing of history. The database is divided into chronological sub-sheets. These are the blocks. The last line of any block summarizes all of the data in the block, and — and this is pretty important — appears as the first line of the next block. If anyone tries to edit a block, the last line will change and will not match the first line of the next block. The network sees this corrupted block and immediately replaces it. This ingenious trick makes it futile to rewrite history and guarantees an unprecedented degree of security. Blockchain was invented by Haber and Stornetta in 1991 but made famous in the Satoshi Nakamoto's bitcoin paper.