Bitcoin is a cryptocurrency:.
In our humble opinion it is more like crypto gold rather than currency, because it doesn't support fast transactions.
One of its main advantages is that the number of coins has known upper bound, preventing inflation.
In addition it is decentralized, making it "government resistant".
According to [1] it was invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto and started in 2009.
Its market capitalization is $713,435,159,726 (7.1 * 10^11) and just for comparison the GDP of Bulgaria is 67.93 billion (68 * 10^9) and Tesla's market capitalization is $800 billion (800 * 10^9).
We find it ironic that the anonymous Satoshi Nakamoto is 23rd richest person in the world on January 4, 2021 :)
Unless otherwise stated, all dates apply to sources of Fri 15 Jan 2021.