What is a preferred domain?
Preferred domains, similar to standardized URLs, are the domains that make up web pages in the search engine index. In search engine search results, links to web pages have www and non-www URL patterns (for example, http://www.seowhy.com and http://seowhy.com). The preferred domain is the format we want the site to show in search results.
Setting the preferred domain name correctly can make the PR value of the website more centralized and accurate.