Bitcoin is a decentralized cryptocurrency created in 2009 by a pseudonymous person (or group of people) named Satoshi Nakamoto. The original Bitcoin whitepaper, titled “Bitcoin: A Peer-to-Peer Electronic Cash System'', was published in 2008 and outlines the proposal for and mechanics of the Bitcoin blockchain.
Unlike for fiat currencies, there is no government or central bank controlling and issuing Bitcoin. Bitcoin is censorship-resistant and was algorithmically designed so that there is a finite supply of 21 million coins. Due to its scarcity, Bitcoin has been lent the name “digital gold.” You can use the Bitcoin blockchain to transact on a peer-to-peer network without going through traditional intermediaries such as banks. The Bitcoin network is run by thousands of computers distributed around the world. Because of the decentralized nature of Bitcoin’s blockchain, all transactions can be transparently viewed by either having a personal node or by using blockchain explorers that allow anyone to see transactions occurring live. 
As the preeminent cryptocurrency today, Bitcoin is considered by many as a formidable alternative asset to gold and fiat currencies.