What is a blockchain?
A plain-English explanation

Start with the problem it solves

Imagine you and a friend both claim to own the same $20 bill. In the physical world, whoever is holding it wins. In the digital world, it's trickier — digital information can be copied. So how do you create digital money that can't be spent twice by the same person?

Banks solve this by keeping a central ledger — one master record of who owns what, controlled by the bank. If you send $20 to a friend, the bank deducts it from your balance and adds it to theirs. You trust the bank to keep the record honest.

Bitcoin's inventor Satoshi Nakamoto asked a different question: what if you could have the ledger without the bank? What if the record of who owns what was maintained by everyone, simultaneously, in a way that nobody could cheat?

That's the blockchain.

What a blockchain actually is

A blockchain is a ledger — a record of transactions — stored simultaneously on thousands of computers around the world. Every time a new batch of verified transactions is ready, it gets bundled into a block and added to the end of the existing record. Each block is cryptographically linked to the one before it. That linked chain of blocks is the blockchain.

The critical property: once a block is added, it cannot be altered. Each block contains a mathematical fingerprint (called a hash) of the block before it. Change anything in an old block, and its fingerprint changes — which breaks the link to the next block, and the next, all the way to the present. An attacker would have to redo every block after the one they changed, on thousands of computers simultaneously, faster than new blocks are being added. It's not possible in any practical sense.

Who holds all these copies?

Thousands of computers called nodes each hold a complete copy of the Bitcoin blockchain. Anyone can run a node — it's free, open-source software, and the full blockchain is publicly downloadable. There's no headquarters, no data center, no CEO who can shut it down.

When a new transaction is broadcast to the network, nodes verify it independently — checking that the sender actually owns the funds, that the digital signature is valid — and if enough of the network agrees it's legitimate, the transaction gets included in the next block. No single authority decides. The majority of the network does.

This is what decentralization actually means in practice: no single point of control, and no single point of failure.

Is the blockchain public?

Yes — completely. Every Bitcoin transaction ever made is visible to anyone on a blockchain explorer such as blockstream.info or mempool.space. You can look up any wallet address and see every transaction it has ever sent or received.

What you won't see is names. Wallet addresses are long strings of letters and numbers — pseudonymous, not anonymous. The transactions are public, but connecting an address to a real person requires information that lives outside the blockchain. This is why Bitcoin is described as pseudonymous rather than fully anonymous.

For merchants, this transparency is useful: you can verify any payment arrived by checking the blockchain directly, without relying on any intermediary to confirm it.

Does every cryptocurrency use the same blockchain?

No. Bitcoin has its own blockchain. Ethereum has a separate one. Solana runs on another. Each is independent, with its own rules, speed, and security model. A Bitcoin transaction doesn't appear on Ethereum's blockchain, and vice versa.

"Blockchain" is sometimes used as a generic buzzword for anything crypto-related, which creates confusion. More precisely: each major cryptocurrency operates on its own blockchain. When OrangeTill supports multiple coins, it's interacting with multiple independent networks simultaneously.

Why it matters for merchants

When a customer pays you in Bitcoin, the transaction goes directly onto the blockchain — not through a card network, not through a bank, with nothing in the middle taking a percentage or delaying settlement.

The blockchain is also why Bitcoin payments are final. Once a transaction is confirmed and buried under subsequent blocks, reversing it is computationally impossible. This is the source of both benefits and responsibilities: no chargebacks ever, but also no reversals if something goes wrong. Understanding this property is foundational to everything else about accepting Bitcoin.