A decentralized digital currency without a central bank or single administrator, Bitcoin was released as an open-source software created as a reward for a process known as mining. Bitcoin offers the promise of lower transaction fees than traditional online payment mechanisms and is operated by a decentralized authority, unlike government-issued currencies. As the earliest cryptocurrency to meet widespread popularity and success, Bitcoin has inspired a host of other projects in the blockchain space. Bitcoin charts high on popularity, and has triggered the launch of hundreds of other virtual currencies collectively referred to as Altcoins.
Scarcity is baked into the system; there will be a maximum of 21 Million Bitcoins by 2140.
Every 4 years, the number of new bitcoins mined every goes down by half.