How can a company be valued at billions, but not make any profit?

Slack Technologies, a messaging service used by companies across the world, has been valued at around 16 billion dollars. It's one of several high-profile tech companies, including Uber and Lyft, going public this year.

But plenty of companies which are valued at billions are yet to make a profit.

The BBC's Consumer Correspondent Colletta Smith explains why.

Produced by Bryony MacKenzie

Edited by Sam Everett