Basically, though you might have surmised from context, it's a bunch of bloggers going, "Oh yes. I will write about X topic on/near Y day." And they do. And then there is a hub post to interconnect all the blog posts.
TBH, my blog doesn't get enough traffic to be 100% ideal for this. But since it looks like there are no bigger blog carnivals for this... I'd rather do it small than not at all.
Thanks for writing! (Can you email me at firstname.lastname@example.org to confirm -- just so I have all the participants in one place?)