Mohit Mamoria has written a 3500-word guide in plain English to understanding Blockchain.
Unlike every other post on the internet, instead of first defining the Blockchain, we’ll understand the problem it solves.
Best explanation I’ve read so far.
Speaking of Blockchain, things could go very wrong for Bitcoin on August 1st due to a chain split:
Do not trust any payments you receive after Tue Aug 01 2017 00:00:00 GMT until the situation is resolved. No matter how many confirmations the new payment says it has, it can disappear from your wallet at any point up until the situation is resolved.