The blockchain is Bitcoin’s public record - an open, chronological, and immutable ledger of every transaction ever made. It’s not a database stored on one server - it’s a distributed system, run by thousands of nodes worldwide, all keeping an identical copy. No one controls it. No one can change it. And everyone can verify it.

Here’s the idea: every 10 minutes, a new “block” of transactions is confirmed and added to the “chain” of all previous blocks. Each block contains a batch of transactions, a timestamp, and a cryptographic link (a hash) to the block before it. This creates a chain of trust that goes all the way back to the genesis block in 2009.

Try to change anything - even a single number in one old transaction - and the cryptographic links break. The entire chain rejects it. That’s what makes it immutable. It’s not just history - it’s mathematically locked-in.

The blockchain is what allows Bitcoin to function without a central authority. It’s the source of truth. It’s where you prove you own your coins. It’s where miners compete to add the next page. And it’s where every sat ever spent is forever etched into time.

TL;DR: The blockchain is Bitcoin’s decentralized ledger - a chain of blocks containing all confirmed transactions. It’s transparent, tamper-proof, and the backbone of the Bitcoin network.