It looks like Valve has registered for the Steam.tv domain, as SteamDB developer Pavel Djundik first saw. If you look at the website's source data (which can be done by pressing F12 in Chrome), Djundik found that Steam.tv is probably a real Valve product as steamcommunity.com has its security certificate. This SSL certificate is from August 14, three days ago. And now, after I've posted this story, Steam.tv has started sending a live stream of Dota 2.
I've asked Valve to ask for details of what this product is, and I'll update that story if and when I get an answer.
(yes, it's real)
̵1; Pavel Djundik (@thexpaw) August 17, 2018
But it's easy to imagine that this is a new homepage for Steam's integrated streaming functionality. You can now stream games to Steam, but these live videos run in the Steam app and are not as easy to broadcast on the internet as competitors like Twitch and YouTube.
And as ResetEra forum user JaseC pointed out The certificate belongs to steamcommunity.com and not to steampowered.com (Valves Store website) makes it more likely that this is something like Twitch. Steamcommunity.com is the social hub of Valve and has so far edited its live video initiative.
If Valve plans its own video livestreaming hub, which you can easily visit in browsers, that would be consistent with some other recent updates. Earlier this summer, the company redesigned its chat system to become more akin to competitor Discord. If it chases other games services, it would make sense that it wants a piece of Twitch as well.
Finally, Steam.tv was completely empty except for a bold text above, the "Welcome" said to steam.tv. "But since Djundik tweeted about it (and I emailed Valve to ask for answers), this text disappeared, which has now been replaced by the livestream I mentioned earlier.