From a Stewart Butterfield profile
"Now many eyes are on Slack and how it performs after going public. The company is planning a “direct listing,” where it will not issue new shares to sell, but simply let its shares start trading on a stock market. Its share price will be set solely by demand from public-market investors.As Slack Prepares to Go Public, Its C.E.O. Is Holding His Tongue | NYT
Slack also faces a crucial test as it transitions from a viral chat app to a more traditional operation selling workplace technology to global corporations. It will be no easy task as Mr. Butterfield deals with competition from Microsoft, which offers a product called Teams, and as Cisco and Facebook push similar tools. Slack is small compared with those giants; on Friday, it disclosed that it lost $32 million in the first quarter, while revenue rose 67 percent from a year ago to $135 million."