Now these days, inbounds links are the one of most important factor for getting a high keyword ranking, the most search engines are ranking their search result on the link popularity from your site. Not the quantity from the links, but the quality of those links is important.

The search engines are smart though, in that they are now starting to look at not only the number of links pointing to your site, but the type of links they are. The types of links can be viewed in two ways:

1. Links pointing to your site from other popular sites can indicate that your site is of better quality and deserves higher ranking.
   That is, a handful of good quality links, with some engines, is better than 100 links from sites that are not popular.
2. Some search engines can check the content of the sites linking in to your site (and in some cases, the content of the sites you link out to).
   Therefore, if a gardening site is pointing to yours, this could be seen as saying your site is about gardening in some way. If the content on your site is about gardening, then this will increase that theme even more and you may be ranked higher on gardening keywords.

Quality links means links from related pages and with high rankings in search engines. Building Quality and Relevant back links is a dual advantage where you attract vistors from the reciprocal linking site and simultaneously boost your websites Page Rank.