A "unicorn" is a venture-capital-backed private startup with a valuation of at least $1 billion. The term was coined by venture capitalist Aileen Lee in 2013 to reflect how rare such companies once were. Today, there are over 1,000 unicorns globally, reflecting the massive influx of venture capital over the past decade.
The founders and early employees of unicorn companies hold significant paper wealth — net worth that exists on paper but cannot be accessed until the company goes public or is acquired. This is why some tech founders appear extremely wealthy on paper years before they can actually liquidate their holdings.
"Decacorns" (valued at $10B+) and "hectocorns" ($100B+) are rarer subsets of this category.