Bitcoin (BTC): What It Is and How It Works

History of Bitcoin

Bitcoin started as a nine-page paper. On October 31, 2008, Satoshi Nakamoto published Bitcoin: A Peer-to-Peer Electronic Cash System, describing digital cash that two people could exchange directly, with no financial institution in the middle. The problem it solved was double-spending: making sure the same digital coin cannot be spent twice when there is no central ledger keeper.

The network went live on January 3, 2009, when the genesis block (block 0) was mined. Its first transaction carries a headline from that day's edition of The Times: “Chancellor on brink of second bailout for banks”, widely read as a comment on the banking crisis of the time.

Nakamoto's identity has never been confirmed. The name faded from public development in the network's early years, and Bitcoin has since been maintained by independent open-source contributors. No company or foundation controls the protocol.

How Bitcoin works

Bitcoin combines four ideas: public-key cryptography, a shared ledger, a peer-to-peer network and an economic incentive that keeps everyone honest.

1. Keys and addresses. A crypto wallet holds private keys. Each private key controls the coins sent to its matching address, and spending them requires a digital signature only that key can produce.
2. Broadcasting. A signed transaction is sent to the network, where thousands of independent nodes check it against the rules (valid signature, no double-spend) and hold it in a waiting area called the mempool.
3. Mining. Miners collect pending transactions into a candidate block and race to find a SHA-256 hash below a target value. This is proof of work: finding the answer takes enormous computation, but anyone can verify it instantly.
4. Adding the block. The first miner to find a valid block broadcasts it, nodes verify it and add it to their copy of the blockchain. The miner receives the block subsidy plus the fees of the transactions inside.
5. Confirmations. Every new block on top of a transaction adds one confirmation. The deeper a transaction sits, the more work an attacker would have to redo to reverse it, which is why large payments often wait for several confirmations.

The protocol targets one block about every 10 minutes. Every 2,016 blocks, roughly two weeks, the mining difficulty adjusts so that block times stay near that target whether miners add or remove computing power.

Bitcoin tracks coins as unspent transaction outputs (UTXOs). A wallet balance is the sum of the outputs its keys can spend, not an account balance kept by anyone. Rules are enforced by the nodes that validate blocks, not by miners alone: a block that breaks the rules, for example by paying the miner too much, is rejected however much work went into it. That split between the work of miners and the checks of nodes is the heart of Bitcoin's consensus mechanism.

A transfer in practice: to send some BTC from a cold wallet, the owner enters the recipient's address and signs the transaction with their private key on their own device. The transaction spreads across the network, a miner includes it in a block, and every block added on top makes it harder to reverse; many services wait for a few confirmations before treating a payment as final. Unlike a bank transfer, this works 24/7, on weekends and holidays, and the fee depends on the transaction's size in the block and on network demand, not on the amount sent. Long-term holders who ride out volatility instead of trading are often described with the community slang HODL.

Bitcoin supply: 21 million and the halving

Bitcoin's issuance schedule is written into the protocol. New coins enter circulation only through the block subsidy paid to miners, and that subsidy halves every 210,000 blocks, about every four years.

Because the subsidy keeps halving, total issuance converges on just under 21 million BTC; rounding at the smallest unit means the round number is never quite reached. That smallest unit is the satoshi, one hundred-millionth of a bitcoin (0.00000001 BTC), so people can hold and send small fractions of a coin.

The last new coins are expected to be mined around the year 2140. After that, miners will be paid only through transaction fees. The share of the supply already issued, and the coins believed lost for good, are tracked as circulating supply, which anyone can check against the public chain. The live Bitcoin price and market data are updated continuously on the spot page.

What Bitcoin is used for

• Peer-to-peer payments. Anyone with a wallet can send BTC to anyone else, across borders, at any hour, without asking a bank for permission. Settlement on the main chain takes minutes rather than days.
• Savings outside the banking system. Many holders treat bitcoin as a long-term store of value and describe it as “digital gold” because its supply is fixed. The comparison is a narrative, not a guarantee: bitcoin has been far more volatile than gold.
• Fast small payments. The Lightning Network, a layer-2 system built on top of Bitcoin, lets users open payment channels and send small amounts almost instantly for very low fees, settling back to the main chain later.
• Institutional exposure. Spot exchange-traded products, company treasuries and government proposals such as a strategic bitcoin reserve give investors and institutions ways to hold BTC directly or indirectly.
• Data and tokens on Bitcoin. Ordinals (2023) and Runes (2024) use Bitcoin block space to inscribe data and issue tokens, a use that developers still debate.

Bitcoin's scripting language is deliberately limited, so complex applications such as lending markets usually run on other chains and reach BTC through wrapped bitcoin tokens.

Bitcoin vs. Ethereum and blockchain

Bitcoin is often confused with the technology it introduced and with the networks that followed it.

Bitcoin vs. blockchain. A blockchain is the data structure: blocks of transactions linked by cryptographic hashes. Bitcoin is the first network that made one work in the open, and bitcoin in lower case usually means the currency unit on that network. Thousands of other blockchains now exist, and most coins other than bitcoin are grouped together as altcoins.

Copies and forks. Because Bitcoin's code is open source, anyone can copy it and start a new chain. Bitcoin Cash, which split off in 2017 over block size, and Litecoin, launched in 2011 from modified Bitcoin code, are two well-known relatives. They are separate assets with their own rules and prices.

Risks to understand

• Volatility. BTC has repeatedly gained and lost a large share of its value within months, and past price moves say nothing reliable about future ones.
• Irreversibility. A confirmed transaction cannot be undone. Coins sent to a wrong address or to a scammer are usually gone for good.
• Custody. Whoever holds the private keys controls the coins. Lost keys cannot be recovered by anyone, and coins left on a third-party platform depend on that platform's security and solvency.
• Scams. Fake giveaways, impersonation and “guaranteed return” schemes routinely borrow Bitcoin's name. Checking every claim yourself, the idea behind DYOR, is the basic defense.
• Regulation and tax. Rules for owning, trading and reporting bitcoin differ from country to country and keep changing.
• Energy use. Proof-of-work mining uses a large amount of electricity, which keeps Bitcoin's environmental footprint under debate.

How bitcoin is stored

Bitcoin is not a file on your phone. The coins exist on the blockchain, and a wallet stores the keys that can move them. Choosing a wallet is a trade-off between convenience and security:

• A hot wallet is software on an internet-connected phone, computer or browser. It suits frequent, smaller payments.
• A cold wallet keeps the keys offline, away from malware and remote attacks, and suits long-term holdings.
• A hardware wallet is a dedicated signing device and the most common form of cold storage for individuals.
• A custodial account on an exchange holds the keys for you. It is simpler, but it means trusting a third party.

Most self-custody wallets generate a seed phrase, usually 12 or 24 words, that can restore every key in the wallet. Anyone who sees it can take the coins, so it belongs offline and never in a screenshot, email or cloud note. Modern Bitcoin addresses start with “bc1” and use SegWit or Taproot, which usually makes transactions cheaper than with older address formats.