What is the most valuable unicorn in the world?

Could you please elaborate on the term "unicorn" in the context of this question? Are we referring to a company that is highly valued but not yet publicly traded, or perhaps a metaphorical creature with a mystical value? Assuming we're discussing startups, which particular company do you believe holds the most significant value among those that have achieved the unicorn status? What factors contribute to its valuation, and how does it compare to other similar enterprises?