The search engines determine your page rankings, but you can do things to up your rankings. What is a ranking? Well, it comes down to the position your website when someone searches for terms that are related to what you sell. You do not want to be on the second page of search results or even farther down. You want to be in the top five or so. You could buy a high ranking by paying for a search engine ad, but those can be expensive. Also, people recognize them as ads. Some people buy PBN links to up their page rankings for their business websites.
A PBN is a private blog network. There are thousands and thousands of expired domains that have been around for a long time. The search engines constantly scan the Internet. If they find reputable domains, such as blogs, that have links on them back to your site, then it makes your site look more reputable. That then gets you a higher page ranking. If you then also have great SEO content on your site, then that helps too. Search engines use algorithms to weed out junk sites from getting to the top of search results.
When you do a search for any particular thing, you are likely to end up with thousands of pages of actual results. However, how far down the list do you go to find a site you want to click on? How often do you click to page two of search results? Yes, that is why you want to be toward the top of page one of the results when someone is searching for what you sell. There are tips and tricks to upping your page ranking, but you want to make sure that what you do does not put you at risk of having your domain penalized by the search engines too.