Gabe Newell, co-founder of Valve and überlegend, has revealed a major event that will run on Steam in the coming days. It is called Steam Next Fest and starts on June 16, and you can find the following information on their website:
Announcing Steam Next Fest, a multi-day celebration of upcoming games. Explore and play hundreds of game demos, watch developer livestreams, and chat with the teams about their games in progress, coming soon to Steam.
During these days, Steam users will be able to play tons of different demos, watch live streams and chat with the developers. More information about this spectacle can be found here.