As spotted by SteamDB, The Steam client was released on September 12, 2003.
— SteamDB (@SteamDB) September 13, 2021
Steam’s beta, though, came out even earlier, in March 2002.
Right now, there are over 50,000 games on Steam, with 7,258 of those released this year alone. According to Valve, Steam is enjoyed by around 120 million monthly active users. Despite the growing competition from alternative stores like Epic Games Store, Steam remains distribution platform No. 1 for PC titles.