Cryptocurrency is a digital or virtual currency that operates independently of a central bank and uses cryptography for security. 

It is decentralized, which means that no government or financial institution controls it.

Bitcoin, the first and most well-known cryptocurrency, was created in 2009. 

Thousands of other cryptocurrencies, also known as altcoins, have been created since then.

To record and verify transactions, cryptocurrencies employ blockchain, a distributed ledger technology. This means that rather than a centralized authority, every transaction is verified by a network of users.

Cryptocurrencies, however, are not without risk, values can be extremely volatile, and they are not backed by any physical asset or government guarantee. They are also vulnerable to fraud and hacking.

Overall, cryptocurrency is a new and evolving technology with both advantages and disadvantages. 

Individuals, businesses, and governments all over the world are investigating its adoption and use cases.