well you can always google it.....just for a hint the site having html links pointing to your site are backlinks.
check other sites related to ur site, then contact them must see how much PR is ur website have then contact the owner of the same PR site owner, go slow slow, be in touch with them make good relations for future.
It is website network, you need to own several websites for link building purposes... you can create blogs on different web 2.0 sites too and it would work for network as well.
Finding high PR links can hard and very time consuming. They do work though and give serious ranking improvements, maybe find some expert SEO to build links for you?