What is Off-site Optimization?

Do you know what is mean by Off-site optimization? According to my research, the major thing that gives you Page Rank (How Google judges your importance and sorts your results in comparison to your competitors) is link backs. Like Amazon.com has so many link backs they don't need to define their doctype. They actually do define their doctype.But what is link back? It simply an anchor that links to your site that doesn't originate in your domain, you can generate link backs by asking fellow bloggers to link back to you, or if you are a business ask your vendors and even customers. And you can also link to your blog on forums and stuff and that will count as a link back but however, you need to understand that forums and comments on blogs have been abused by spam links and we have come up with something called NOFOLLOW that will tell search engines not to index stuff that is linked to on the sites comments and forums. Linking to negative pages will decrease your page rank also. It means a negative page linking to you has no effect. You can do On-Site optimize as much as you can and build link backs but only if they are relevant.