Bitcoin is a form of digital currency, often considered the first and most popular cryptocurrency. Created in 2009 by an individual or group of individuals using the pseudonym Satoshi Nakamoto, Bitcoin is based on a technology called blockchain. Here are some key elements to define Bitcoin:

1. Cryptocurrency: Bitcoin is a virtual currency that uses cryptographic techniques to secure transactions, control the creation of new units, and verify the transfer of assets.

2. Blockchain Technology: Bitcoin operates on a blockchain, a decentralized and distributed ledger that records all transactions made in Bitcoin. This technology ensures the transparency, security, and integrity of transactions.

3. Decentralization: Unlike traditional currencies, Bitcoin is not controlled by any financial or government institution. It is managed by a peer-to-peer network where each participant can contribute to maintaining the blockchain.

4. **Limited Supply**: The number of Bitcoins that can be created is limited to 21 million, introducing a scarcity similar to that of precious metals like gold. This feature is intended to reduce the risk of inflation.

5. **Anonymous Transactions**: Bitcoin transactions do not require personal information and are recorded under alphanumeric addresses, providing a certain level of anonymity.

6. **Volatility**: The price of Bitcoin is known for its volatility, meaning it can experience significant price fluctuations over short periods of time.

7. **Uses**: Bitcoin can be used for various types of online purchases, as an investment (often considered a store of value), or for cross-border money transfers.