Games can't be designed in a vacuum. In order to make a game that people will want to play, you'll need people to play it! The Playtest Co-op is a space for tabletop game designers to refine their own games and help others refine their games in turn.
The current tools and resources for designers are rather ad-hoc and unevenly distributed. Designers living in cities (especially some cities like Seattle, New York, and Raleigh) have many more resources in their local communities for playtesting. That is awesome and should continue, but the goal of the Playtest Co-op is to provide that same sort of community for everyone. The site aims to be accessible to those in rural, remote, or otherwise underserved areas and give them tools to test their games. During a pandemic, this is especially important to give folks an online space to share their games.
The site is currently closed source, but the bug/feature tracker is available here