Think of a blockchain as a digital record book. Instead of keeping records in one place (like a single computer or server), the information is copied and spread across a network of computers. Each page of this record book is called a "block," and they're all linked together in a chain. Whenever new information is added, it's put into a new block, and everyone's copy of the record book updates. This makes it really hard to change older information because you'd have to change it on every single copy at the same time. So, blockchain is like a shared, super-secure digital diary that a bunch of people have copies of and can write in, but no one can easily change what's already been written. This is why it's used for things like digital money (crypto currencies) or for NFTs and keeping track of who owns what.