A cryptocurrency is a digital asset recorded on a blockchain: a shared ledger copied across thousands of computers, so no single company controls it.
- Bitcoin (BTC) was the first. Its supply is capped at 21 million coins, and new coins are released on a fixed schedule that halves about every four years.
- Ethereum (ETH) is a blockchain that runs programs called smart contracts. Many other tokens and apps are built on it.
- Stablecoins like USDC and USDT try to stay worth $1. They are used to move dollars around crypto markets.
- Altcoins is the catch-all name for everything else. Most are far smaller and far riskier than Bitcoin.
Crypto trades 24 hours a day, 7 days a week. There is no closing bell and no circuit breaker, so prices can move a lot while you sleep.