Valve's platform now has one billion accounts and 90 million active users per month.
As the site points out, this doesn't meant here are one billion people with Steam accounts. A significant portion of these accounts are likely inactive, or belong to players with multiple accounts.
Back in October 2018, Valve reported that Steam has 47 million daily active users - that's 90 million per month - and that those players make around 1.6 million purchases between them every month.
That was shortly before the announcement of the Epic Games Store which caused waves following the revelation that it would beat Valve's 70/30 revenue split with developers with its more generous 88/12. This resulted in a number of exclusivity deals that have not gone down well with the community.
Epic CEO Tim Sweeney has since said that the Epic Games Store would stop signing these deals if Steam matched its revenue share offer.
During December 2018, Valve banned over 600,000 Steam accounts making for a record number of bans on the platform, and most of these were related to CG:GO.