Links are the main determinants of ranking behavior. Both site architecture and content are big players in achieving search engine friendliness, but when it comes to the mechanism for ordering results, external links are the critical metric.
Links are also multidimensional in their impact. For example, the strength of a site’s inbound links determines how frequently and how deeply a site is crawled.
In addition, each link’s context (its location within the page, anchor text, surrounding text, etc.) is taken into account when determining relevance. And links can convey trust, helping to overcome potential spam designations (which can torpedo a site’s SEO success).
There are two critical points to remember regarding link building:
Link building is a fundamental part of SEO. Unless you have an enormously powerful brand (one that attracts links without effort), you will fail without it.
Link building should never stop. It is an ongoing part of marketing your website.