Please help: beginner website CPM advertising

Hi, first time poster. I’m hoping to get some help with some questions I have.

First, I know that there are many affiliate programs that work on CPM. That’s what I want. But are any of these just CPM, so that in theory I could have nobody clicking on the ads and still make some money from advertising?

Second, how do these affiliate programs work? I sign up on their site, and then do I pick the banners and ads that go on my site? Or do I then have to contact the specific banners and ads and get them to advertise on my site? I was hoping it would be that the affiliate site has some CPM rate and then I could just take any ads from that site.

Third, is there a way to get CPM advertising without the advertisers really knowing what my site is about? What I mean is, once I join the affiliate site, do the advertisers pick my website to advertise on or do I pick the advertisers?

Fourth, is the CPM rate a rate per banner / advertisement? So, if I put up two banners, then I get double? Three, triple?

Fifth, what is an average CPM rate for a publisher like me?

Thanks so much for any help you guys can give me.