Bitcoin (BTC) is the first decentralized digital currency, created in 2009.
BITCOIN Price Movement 2009 to 2017
It was invented by Satoshi Nakamoto based upon open source software and allows users to make peer-to-peer transactions via the Internet that are recorded in a decentralized, public ledger. Bitcoin has the largest market capitalization by far of all cryptocurrencies, 19 times larger than the runner up Ethereum.
The number of units is capped at 21 million, 16 million of which are available. The cap ensures that inflation won't decrease their value.
When users allocate computer processing power towards the mining of Bitcoins, they are rewarded with transaction fees and newly created coins. Units can be bought or sold against other cryptocurrencies or against fiat currencies like the USD or the EUR at many exchanges, which operate like physical currency exchanges.
Units can also be saved or obtained in exchange for goods or services. TradingView, for example, accepts Bitcoin for annual plan payments, as one of many companies that allow their online products or services to be bought with Bitcoin.