"Crypto" is a common shorthand for "cryptocurrency," which is a digital or virtual currency that uses cryptography for security. Cryptocurrencies are decentralized and operate independently of a central bank or government, using blockchain technology to keep a public ledger of all transactions. Some of the most well-known cryptocurrencies include Bitcoin, Ethereum, and Litecoin. While cryptocurrencies have been around since the late 2000s, they have gained increasing popularity and mainstream attention in recent years.