[twetge]

private blog network.

An seo company will buy a bunch of recently expiring domains related to a specific topic, and do it in a way that hides who the owners are. They build blogs on these sites, and fill them with the lowest grade content. I've see stuff that's "spun" (plagiarized content where a percentage of words have been replaced with synonyms, so that it appears original) and other stuff that's farmed out to writers in developing countries who work for pennies (A lot of articles with no real substance, written in poor english.)

The owner then links all the blogs to each other, so they appear to have domain authority. Then they sell back links to their customers. This fools Google into thinking your website is trustworthy (because everyone is linking to it) and you get better placement in search results.

In short, its a way anyone can buy popularity online.