All Subdomain pages can show as backlinks?

How come subdomains convert to be backlinks?

[funsapple]

When i was doing link exchange, i came across a website which have 2000 over back link in google and 90000 back link in yahoo. Without a thought, i do a link: check and found that most of the back links are actually the subdomain pages. I believe that with such high back links,so its PR=8.
I wonder is it true that the subdomains may help on the quantity of the back links? If yes, is there any rules behind?
amazing.

[edited by: sugarrae at 4:47 pm (utc) on Mar. 16, 2006]
[edit reason] no specifics please [/edit]

[Stefan]

Backlinks are backlinks, whether they're from the same site or not. Any particular page on your site has backlinks that include both internal and external.

As for the PR8, I doubt if it's generated by subdomains (it doesn't really work that way) - more than likely the site has some major links from separate domains.