Valve offers a Steam 2020 Year in Review Report. They look back at last year on the service in words and pictures, offering all sorts of statistics. Here's a bit:

As many of you already know, this past year had more than its share of challenges, with everyone's lives upended by the global pandemic. While Steam was already seeing significant growth in 2020 before COVID-19 lockdowns, video game playtime surged when people started staying home, dramatically increasing the number of customers buying and playing games, and hopefully bringing some joy to counter-balance some of the craziness that was 2020. This has led to new highs for monthly active users (120.4 million), daily active users (62.6 million), peak concurrent users (24.8 million), first-time purchasers (2.6 million per month), hours of playtime (31.3 billion hours), and the number of games purchased (21.4% increase over 2019).