You know a linked list? Then you get the gist. It’s a node, with some data, and a previous. But this is what I missed when I started this, the secret to the chain is SHA-256. Or KECCAK-256 if you’re mining the Ethereum. It’s like SHA-3, but it’s not. Check the medium.com. I’m sure you’ll find a blog post. Know what matters most is that we hash when we link the nodes.
This hashing, if you’re asking, takes a long time by design. That’s why people like to call it “mining”. They’re supplying evidence of work, of stake, and time. It’s called “buy in”.
When you make real tough to grow the chain, you make it real tough to break the chain. And when we all have the chain, we all trust the chain.