Bitcoin is a digital currency created in 2009. It follows the ideas set out in a white paper by the mysterious Satoshi Nakamoto, whose true identity has yet to be verified. Bitcoin offers the promise of lower transaction fees than traditional online payment mechanisms and is operated by a decentralized authority, unlike government-issued currencies. Today's market cap for all bitcoin (abbreviated BTC or, less frequently, XBT) in circulation exceeds $7 billion.

There are no physical bitcoins, only balances kept on a public ledger in the cloud, that – along with all Bitcoin transactions – is verified by a massive amount of computing power. Bitcoins are not issued or backed by any banks or governments, nor are individual bitcoins valuable as a commodity. Despite its not being legal tender, Bitcoin charts high on popularity, and has triggered the launch of other virtual currencies collectively referred to as Altcoins.

[ While Bitcoins are the key player in the cryptocurrency marketplace, as you'll read below, the whole ecosystem is much greater than this one coin. For a detailed explanation of the world of cryptocurrency taught with graphic depictions and simplified example, check out Investopedia Academy's Cryptocurrency for Beginners course. ]