A cryptocurrency is a type of digital money that exists only on computers and uses advanced mathematics called cryptography to keep transactions secure and private. Unlike dollars or euros, cryptocurrencies aren't printed by governments or controlled by banks. Instead, they're created and tracked by networks of computers around the world working together.

Bitcoin, created in 2009, was the first cryptocurrency and remains the most famous. When you own Bitcoin or another cryptocurrency, you don't have coins in your pocket or bills in your wallet. Instead, you have a digital key that proves you own a certain amount, like having a password that gives you access to money stored across thousands of computers.

People can send cryptocurrency directly to each other over the internet without needing a bank in between. These transactions are recorded in something called a blockchain, which is like a public ledger that everyone can see but no one can secretly change.

Cryptocurrencies are controversial. Supporters believe they give people more financial freedom and privacy. Critics worry about their use in illegal activities, their dramatic price swings, and the enormous amounts of electricity some cryptocurrencies require. Some people have made fortunes investing in cryptocurrencies, while others have lost substantial amounts of money when prices crashed.