Bitcoin
Bitcoin is a decentralized digital money and payment system, described in a 2008 white paper and launched in 2009. It was the first cryptocurrency to work in practice without a central bank or company in charge.
How Bitcoin works
Bitcoin is a network of computers, called nodes, that all keep a copy of the same public ledger: the blockchain. Every transaction ever made is recorded there. When you send bitcoin, you sign the transaction with your private key, a secret number only you should know, and broadcast it to the network.
Miners collect waiting transactions into blocks and compete to add the next block using proof of work, a process that requires real computing power and electricity. The winner receives newly issued bitcoin plus transaction fees. Nodes independently check that every block follows the rules, so no single party can rewrite history or create coins outside the schedule.
A fixed supply
New bitcoin are issued only as block rewards, and the reward halves roughly every four years. As a result, the total supply will never exceed 21 million coins. The fourth halving, in April 2024, cut the reward to 3.125 BTC per block. One bitcoin can be split into 100 million smaller units called satoshis, so you never need to buy a whole coin.
What people use it for
Some hold bitcoin as a long-term savings asset, often described as digital gold. Others use it to send value across borders without a bank, or in places where the local currency is unstable. Because it is open, anyone with an internet connection can use it without asking permission.
Risks to understand
The price is highly volatile and has fallen by more than 70 percent from peaks more than once. Transactions cannot be reversed, so sending to a wrong address or a scammer usually means the money is gone. If you hold your own keys and lose your seed phrase, nobody can recover your coins; if you leave them on an exchange, you depend on that company staying solvent and honest. Tax and legal treatment differ by country.
Ask Coach about it
Coach is the AI on AtenaCrypto. It explains crypto with live market data, in plain words.
Can you walk me through what happens step by step when I send bitcoin to someone?Ask Coach →
Frequently asked questions
Who controls Bitcoin?
No single person or company. Its rules are enforced by thousands of independent nodes, and changes require broad agreement among users, developers and miners.
Is Bitcoin anonymous?
No, it is pseudonymous. Addresses are not tied to names on the blockchain, but every transaction is public and can often be linked to people, for example through exchanges that verify identity.
Can Bitcoin be hacked?
The network itself has proven very resilient since 2009. Most losses come from hacked exchanges, stolen keys, phishing and scams rather than from breaking Bitcoin's rules.
Related terms
Learn it step by step
AC Learning explains these ideas in interactive lessons — the first eight sections are free.
Open AC Learning → Create a free accountAll glossary terms · Educational reference only — not investment, legal, tax or financial advice.