What is Bitcoin? A plain explanation

What is Bitcoin, in plain words

What is Bitcoin? It is a form of digital money that you can send to anyone on the internet without a bank in the middle. It was described in a short paper published in 2008 under the name Satoshi Nakamoto, called Bitcoin: A Peer-to-Peer Electronic Cash System. "Peer-to-peer" just means people deal with each other directly, the way you hand someone a banknote.

With a bank transfer, your bank keeps the record of who owns what. Bitcoin replaces that single record keeper with thousands of computers around the world that all keep a copy of the same record. When you send bitcoin, the network checks that you really own it and that you haven't already spent it somewhere else. That second problem, called double-spending, is the main puzzle the original paper set out to solve.

A few words you will see everywhere:

• Bitcoin (BTC): the coin itself, and also the name of the network.
• Satoshi: the smallest unit. One bitcoin is 100,000,000 satoshis, so you never need to buy a whole coin.
• Wallet: the app or device that holds the secret keys that prove the coins are yours.

How the blockchain works

The blockchain is the shared record. Roughly every 10 minutes, recent transactions are bundled into a "block". Each new block contains a digital fingerprint of the block before it, so the blocks form a chain going all the way back to the very first one.

That chaining is what makes the record hard to fake. The whitepaper explains that once a block has been sealed, it can't be changed without redoing the work for that block and every block after it. The longer the chain grows on top of a transaction, the harder it becomes to rewrite.

Think of it as a notebook that thousands of strangers copy, page by page, where each new page quotes the last line of the page before. If someone tried to change an old page, every copy afterwards would stop matching.

What mining is

Mining is how new blocks get added and how new coins come into existence. Computers called miners compete to solve a maths puzzle that is hard to solve but easy to check. The paper calls this proof-of-work. The first miner to find the answer adds the next block and is paid in two ways:

1. Newly created bitcoin, written into the first transaction of the block.
2. Transaction fees paid by the people whose payments are in that block.

According to Bitcoin.org, a new block arrives about every 10 minutes on average, and the network adjusts the difficulty of the puzzle to keep it near that pace. Mining uses a lot of electricity, which is one of the most common criticisms of Bitcoin.

Why there will only be 21 million

Bitcoin's rules fix the total supply: only 21 million bitcoins will ever be created. The number of new coins created each year is cut in half on a fixed schedule, an event people call the halving. New coins will keep trickling out for decades, getting smaller each time, until the limit is reached. After that, miners are expected to rely on transaction fees.

This fixed supply is why some people compare Bitcoin to gold. It is also different from euros, where the European Central Bank can change the amount of money in the system. Bitcoin.org adds a detail worth knowing: coins in wallets that people lose access to stay on the blockchain but can never be spent again.

Why the price swings so much

Bitcoin pays no interest, no rent and no profits. There is no company behind it and no central bank supporting its value. Its price is simply what the next buyer is willing to pay. Bitcoin.org itself says the price "is still very volatile".

Prices move with news, regulation, interest rates, big holders buying or selling, and plain mood. Because the supply is fixed, a change in demand goes straight into the price.

Big drops are harder to recover from than they look:

A 50% fall followed by a 50% rise leaves you a quarter down. To get back to where you started after halving, the price has to double.

The risks, plainly

• Volatility. As above, falls of half or more can happen. Short-term moves tell you very little about where the price will be later.
• Scams. Crypto is a favourite tool for fraudsters. The UK's Financial Conduct Authority (FCA) describes fake investment websites that "fake prices and investment returns", ads using celebrity images, and follow-up "recovery" offers from the same criminals. Treat any promise of high, quick returns as a warning sign.
• Losing your keys. Bitcoin payments can't be reversed, and there is no "forgot password" button for the blockchain. If you hold coins yourself and lose your secret recovery phrase, or someone else gets it, the coins are gone. Our guide to hardware wallets explains how people protect them.
• Provider failure. If you keep coins with an exchange, you depend on that firm staying honest, solvent and secure.
• Regulation. Rules change. In the EU, the Markets in Crypto-Assets Regulation (MiCA) now requires firms offering crypto services to be authorised, and ESMA publishes a register of them. In the UK, a new FCA regime is expected to start in October 2027. Tax treatment also differs by country.

How Bitcoin compares with other places for your money

Bitcoin is not a savings account, and it is not the same as a diversified fund. An index fund owns pieces of hundreds or thousands of companies that make profits. A savings account pays interest and, in the EU, bank deposits are guaranteed up to €100,000. Bitcoin offers neither of these.

That is why many people who do buy Bitcoin treat it as a small, speculative extra on top of the basics, not as the foundation. If you are still building your safety net, the order that usually makes sense is an emergency fund first, then long-term investing such as low-cost ETFs, and only then any speculative money.