What is a unicorn startup worth a billion dollars?

Can you elaborate on the term "unicorn startup" and its significance in the world of finance and cryptocurrency? Specifically, how does a startup achieve the status of being valued at a billion dollars or more? What factors contribute to this high valuation, and how does it impact the broader market and the company's future prospects? Additionally, how do investors and venture capitalists perceive these unicorns, and what role do they play in fueling their growth?