Bitcoin is a decentralized digital currency that was created in 2009 by an anonymous person or group of people using the pseudonym Satoshi Nakamoto. It was the first cryptocurrency and remains the most well-known and widely used.

Here are some key points about Bitcoin:

1. Decentralization: Bitcoin operates on a decentralized network known as the blockchain, which is a public ledger that records all transactions. This means that no central authority, such as a government or financial institution, controls Bitcoin.

2. Limited Supply: Bitcoin has a limited supply of 21 million coins. This scarcity is built into the system to prevent inflation. New bitcoins are created through a process called mining, where powerful computers solve complex mathematical problems to validate and record transactions on the blockchain.

3. Security: Bitcoin transactions are secured using cryptographic techniques. Each transaction is verified by multiple participants on the network, known as miners, who ensure its validity and prevent double-spending.

4. Anonymity: Bitcoin transactions are pseudonymous, meaning they are not directly tied to the identities of individuals. While transactions are recorded on the blockchain, the identities behind the transactions are not publicly disclosed. However, it's worth noting that Bitcoin transactions can still be traced to a certain extent.

5. Volatility: Bitcoin's price is known for its volatility, which means it can experience significant price fluctuations over short periods. This volatility has made Bitcoin an attractive investment opportunity for some, but it also comes with increased risk.

6. Use Cases: Bitcoin was initially designed as a peer-to-peer electronic cash system, allowing individuals to send and receive payments without intermediaries. Over time, it has evolved to have additional use cases, including a store of value (akin to digital gold) and as a means of transferring value across borders.

7. Adoption and Recognition: Bitcoin has gained significant adoption and recognition since its inception. Many businesses, both online and offline, accept Bitcoin as a form of payment. Additionally, numerous countries have developed regulations around cryptocurrencies, while some have embraced Bitcoin more openly than others.

It's important to note that the cryptocurrency landscape is continually evolving, and while the information provided here is accurate up to September 2021, there may have been new developments or changes in the Bitcoin ecosystem since then.