There is no shortage of explainer videos attempting to outline the basics of how blockchain works.
The trick is to explain some fundamental concepts in a simple fashion; albeit at the risk of oversimplifying to the point of being factually incorrect.
This video does a competent job, although it focuses on the Bitcoin blockchain. Certainly the Bitcoin blockchain is ubiquitous, due to its association with its famous crypto asset. However, blockchain as the world will know it, will be built upon any other network except Bitcoin, since that one is a single-use ledger.
Getting back to the video principles: Picture a spreadsheet that is duplicated thousands of times across a network of computers. Then imagine that this network is designed to regularly update this spreadsheet and you have a basic understanding of the blockchain.
Information held on a blockchain exists as a shared — and continually reconciled — database.
The blockchain database isn’t stored in any single location: it’s stored on many computers and the records it keeps are public and easily verifiable. (At least on a public blockchain. Such is not the case on a private blockhain).
A key benefit is that no centralized version of the network data exists for a hacker to corrupt.
Here on the verge of 2019, it’s not a perfect technology. Hence, there are many developers working to establish blockchains that are closer to the promise of this technology: faster, less expensive, more transparent and immutable transactions.