https://www.theregister.co.uk/2018/05/25/square_twitter_founders_other_company/

Profile Ever wandered into a bank on weekday morning and marvelled at length of the queue? In a supposedly cashless era, it's the sight of a nation of shopkeepers depositing its cash.

Co-founded by Twitter CEO Jack Dorsey, Square brings credit card payments to merchants who'd find them otherwise prohibitively complicated and expensive, rolling three separate procurement tasks into one. Square couldn't really be more different to Twitter (a global IRC channel with hygiene issues) as it has such an obvious, practical everyday value proposition, and is in a complex competitive market.