A very good and simple explanation how Bitcoin works which is also a great explanation for the basics of Blockchain. Bitcoin is a digital currency that is the largest application of Blockchain technology.
The block chain is a shared public ledger on which the entire Bitcoin network relies. All confirmed transactions are included in the block chain. This way, Bitcoin wallets can calculate their spendable balance and new transactions can be verified to be spending bitcoins that are actually owned by the spender. The integrity and the chronological order of the block chain are enforced with cryptography
The site contains much more than the basic explanation. You can find much more information and resources to further your knowledge