What is a Private Blog Network (PBN)?
A private blog network (PBN) is a group of websites that link to one another. Bloggers often create them by purchasing expired or auctioned domain names with existing authority.
Since search engines use backlinks to determine a site’s authority and rankings, it is common for a single blogger or a small group of bloggers to buy up these domains and update them with backlinks pointing to their main site. That way, the sites pass link juice to their main site and increase their rankings.
That said, private blog networks are against Google’s guidelines. Google considers them a link scheme and could deindex sites that use them. However, bloggers using private blog networks typically put a lot of effort into hiding their ownership to avoid Google’s penalty.