What Is Bitcoin?

What is Bitcoin? It is a form of digital money that works without a bank, a government or any company in charge. Balances are recorded on a public ledger, the blockchain, that thousands of computers around the world keep in agreement. It was described in a 2008 paper under the name Satoshi Nakamoto, the network went live in January 2009, and every other cryptocurrency has been compared with it since.

The problem Bitcoin set out to solve

Digital files can be copied endlessly, which made digital money hard: what stops someone spending the same coin twice? Before Bitcoin, the answer was a trusted middleman, such as a bank, keeping the record. Bitcoin replaced the middleman with a shared record that everyone can check and nobody can secretly change. Once a payment is buried under enough later blocks, rewriting it would require outspending the rest of the network on computing power.

Mining and blocks

New transactions are gathered into blocks roughly every ten minutes. Miners compete to add each block by running specialised machines that make trillions of guesses at a mathematical puzzle. The winner adds the block and receives a reward: newly created bitcoin plus the fees attached to the transactions inside.

The network adjusts the puzzle's difficulty about every two weeks so that blocks keep arriving at around ten-minute intervals, however much mining power joins or leaves. That steady pace is what makes Bitcoin's supply schedule predictable.

21 million coins and the halvings

The Bitcoin software sets a hard limit of 21 million coins. They are released gradually through block rewards, and the reward is cut in half roughly every four years, an event called the halving.

The next halving is expected around 2028. A quick sum shows the current pace: at about one block every ten minutes there are 24 × 60 ÷ 10 = 144 blocks a day, and 144 × 3.125 = 450 new bitcoin a day. Halvings reduce the flow of new coins, but they do not determine the price, which depends on how many people want to buy and sell.

Satoshis: buying a fraction

One bitcoin is divisible into 100,000,000 units called satoshis, or sats. You never need to buy a whole coin. With an illustrative price of $80,000 per bitcoin, $50 buys 50 ÷ 80,000 = 0.000625 BTC, which is 62,500 satoshis, before any fee.

How sending bitcoin works

1. Your wallet creates a transaction saying which coins move to which address, and signs it with your private key.
2. The transaction is broadcast to the network and waits with others in a queue.
3. A miner includes it in a block, usually choosing transactions that pay higher fees first.
4. Each later block adds another confirmation; many services wait for several before treating a payment as final.

Bitcoin addresses look different from the Ethereum or Tron addresses covered in our USDT lesson. Always check that you are sending bitcoin to a bitcoin address; sending it to an address on another network can mean losing it.

Why the price swings so much

Bitcoin has no earnings, dividends or central bank behind it. Its price is set entirely by what buyers will pay. Supply is fixed, so shifts in demand, driven by news, regulation, interest rates, the arrival or departure of large investors and plain enthusiasm or fear, feed directly into the price. It has risen and fallen by very large percentages several times, and there is no reason to assume the pattern has ended.

Some people see Bitcoin as a long-term store of value, sometimes described as digital gold. Others see it as a speculative asset with no intrinsic value. This library takes no side and makes no forecasts; the useful point for a beginner is that both views exist and the price can move a long way in either direction.

Bitcoin compared with a bank transfer

Neither is simply better. Bitcoin removes the middleman and the opening hours; a bank adds protections and the chance to put mistakes right.

Ways people hold bitcoin

• On an exchange: easy, but you rely on the exchange's security and solvency.
• In a self-custody wallet: you control the keys, and you alone are responsible for protecting the recovery phrase.
• Through a fund or exchange-traded product in countries where these are available: you own a fund share, not the coins, and pay the fund's charges.

Whichever route, the costs are covered in the trading fees lesson and the platform checks in our ten-point checklist. To test what a price move would mean for a trade, including fees, use the crypto profit calculator.

Keeping bitcoin safe

• Use app-based two-factor sign-in on any platform account, never text message alone where a better option exists.
• If you hold your own keys, write the recovery phrase on paper or metal, store it offline and never photograph it or type it into a website.
• Check the receiving address in full before sending, and send a small test amount first for large transfers.
• Be suspicious of anyone who contacts you about your bitcoin, however official they sound.
• Keep only what you need for active use on an exchange.

The scam lesson describes the tricks that target bitcoin holders in more detail.

Common misunderstandings

• "Bitcoin is anonymous." Every transaction is public. Addresses are not names, but they can often be linked to people.
• "You can mine it on your phone." Mining now needs specialised hardware and cheap electricity; phone "mining" apps do something else, as our lesson on free crypto mining apps explains.
• "Someone controls it." No single party does. Changes to the rules need broad agreement from the people who run the software.
• "Lost coins can be recovered." Without the private key, they cannot.

Sources

• Bitcoin whitepaper, 2008
• Bitcoin Core protocol documentation