"Une image vaut 1000 mots"
A unicorn is a start-up company valued at over $1 billion. Canadian tech unicorns are known as narwhals. A decacorn is a word used for those companies over $10 billion, while hectocorn is the appropriate term for such a company valued over $100 billion. According to VentureBeat, there were 229 unicorns as of January 2016. The largest unicorns included Uber, Xiaomi, Airbnb, Palantir, Snapchat, Dropbox and Pinterest. As of October 2015, Uber was valued by Fortune at US$51 billion.
Bill Gurley, a partner at Benchmark predicted in March 2015 and earlier that the rapid increase in the number of unicorns may presage what he has termed a "risk bubble" that will eventually burst, leaving in its wake what he terms dead unicorns.
read more : https://en.wikipedia.org/wiki/Unicorn_(finance)