Domains vs subdomains in SE ranking

[admin]

I am seeking to understand if search engines treats subdomains as a complete website or as a page of the main domain name. I have a website <!-- m --><a class="postlink" href="http://portalshops.com">http://portalshops.com</a><!-- m --> and users get web portals using subdomains eg <!-- m --><a class="postlink" href="http://greg.portalshops.com">http://greg.portalshops.com</a><!-- m --> . Would each subdomain be seen a a link of the main domain name or as an independent website linking to portalshops.com? Does subdomains increase ranking in terms of sites linking back to the main domain? Please contribute