Of course, not all links are equal. While link volume is the number of links coming to a specific page of your site, link authority looks at the value of the links. Some sites are more trusted than others. So, if they are more trusted, then links from those sites are worth more. Likewise, some sites are more relevant than others to specific terms. The more relevant a site, the more value is transferred by the link. Well-known and established news sites, government sites (.gov) and university domains (.ac) are examples of sites from which links can carry more weighting. Links form websites that have a higher PageRank also carry more link weight.
Search algorithms also consider relationships between linked sites. By analysing various things, the search engines try to determine if the links are natural links, or if they are manipulative, artificial links created solely for ranking purposes. Manipulated links are worth very little compared to natural links and may even lead to a drop in search engine rankings.
The search engine algorithm will also determine the relevancy of the referring website to the site being linked to. The more relevant the sites are to each other, the better.
Also consider that linking to valuable, relevant external resources can help to improve the visibility of your own site.
