When it comes to back links to your website there really are just two basic kinds. The first kind is links of quality and the second kind is those that are not. Quality links come from Authority sites that are relevant to your websites content.
As an example: If your website is real estate related, you preferably want links to come from real estate related websites. Links within related content or categories scores higher in relevancy to your sight and are weighted heavier in the search engines. Plus, relevant links from sites of Authority are weighted heavier in the search engines.
Back links to your website are really just like votes in an election. With just one little twist, high quality links count much more than poor quality links. As a reference point, one relevant link from an Authority site could easily be worth thousands of poor quality links.
So what is relevance? Relevance is how closely the content between the two linking websites relates to each other. You can get relevance in a couple different ways. You can go to the webmasters of those sites working in the same niche as you and request links. Just keep in mind that these are probably your...