Ok that's good but ... what exactly will be open accessed? Do they keep a lot of what is important or interesting? I really don't know right now. They should have also added the relevancy of that announcement; right now I just don't know what will all be opened, so I hope to find this information in the comments here.

its a huge amount of high quality content. See https://dl.acm.org. The older stuff was opened a few years back.