Search engine optimization (SEO) is a means to streamline your website to rank higher in search engines. One aspect of SEO relies heavily on the assessments of links (what anchor text is used, is it coming from a page with authority, is the link trusted, when what it built, etc.) to sculpt on page relevance and improve search engine rankings.
Search engines use links (both internal and external links) to assess context both within your website and to your website from other sites and what ranking factors and values your website receives and passes on to others.
Every link from within your own website represents a fraction of the total volume of link flow that moves throughout your site. Much like a moving target, harnessing this flow of link current is crucial to impart vital ranking factors from page to page and consolidate them to areas designed for conversion (your top landing pages).
Internally there is allot more freedom to link as you please, but when dealing with off page factors (link building) having a diverse array of links is far more important; which in turn exposes your website to their broad cross-section of supporting websites. As an example visit Walk2Web.com to view the link graph in action.
This is known as link diversity and is a crucial metric in concentrating on page and off page ranking factors. Another consideration is being aware of link clusters. If a cluster of links all appear within a specific time frame, it can represent automation or popularity.
This is a contingent of link velocity (the rate in which you gain or lose links); the idea is to create a sustained variance in link diversity from a plethora of sources over time. Since each type of link passes a different type of value this in turn impacts your web pages position for the cited references in the link /anchor text.
Through the combination of forward linking (to other sites) and back links (from other sites) the synergy of both is integral for (a) ranking higher with less effort in contrast to non-optimized sites and (b) to establish your website as a hub or authority site.
Another consideration for link building is the link/churn rate /factor of pages getting archived or diminishing from lack of link prominence. The first link on a page is the typically the strongest. After that, each link diminishes in value as you reach the lower areas of the footer of the page (based on a chronological order from left to right since spiders read data like humans).
In addition, to keep ranking factors at optimal levels, one should cap outbound links to 40 outbound links or less per page (or consider no-following some links) to provide enough link flow to other areas of a site.
This is why the number of links from one page to another also impacts the degree of link flow the receiving page assumes. Combine this with the fact that links from blog posts, article repositories and many other forms of link building methods have a tendency to get archived rather quickly. This means that until links from pages come out of the dip (indexed/archived then passing 100 link flow). This can take months in most instances; therefore, you are better off focusing on quality one way links from other sites that will remain intact for extended periods.
Just because link diversity is important for SEO does not preclude the emphasis of on page SEO, which is the primary method for impacting rankings. Link building from other sites is a necessary step, but without maximizing the way the link flow is shared within a site or removing any penalties you are only functioning on 50% of the resource available for you to sculpt, concentrate and unify for a common goal.