A backlink is a link from one website pointing to another website (or web page), usually in the form of a hypertext link (this is an example of a hypertext link). Backlinks are incoming links to a website or web page from another website not related to the first. Backlinks are also known as "inbound links." We just gave Wikipedia a backlink by linking the text "hypertext link" to a page on the Wikipedia website (https://en.wikipedia.org/wiki/Hyperlink).
Generally speaking, the more backlinks you have pointing from other websites to your website, the more trusted your website will be to the major search engines. Backlinks are a form of "popularity", and each backlink is a vote about the value and worthiness of your website, or web page.
Link Signals - Backlinks are a valuable source of “link signals” determined by search engines, like Google. Thus, backlinks determine your blog’s popularity and therefore its value in Google.
Popularity - In theory, the more popular your website (blog) the more links will be pointing to your website and visa verse. The number of backlinks and the individual value of each backlink will determine your website’s trust, authority, and therefore your expertise.
Specific Popularity - If your backlinks are coming from topic related website sources they tend to validate your website’s authority and trust in your space. The type of backlinks your blog gets matter.
Anchor Text and TrustRank - If good backlinks point to a specific keyword or key phrase that defines you and your blog, there is a higher likelihood that you will gain trust in the search engines, especially Google. But if the backlinks pointing to your websites keywords are from spammy websites or web pages, the backlinks will hurt your reputation and trust in Google.
Thus, spammy backlinks can harm your website’s trust and rank in the search engines. Spammy backlinks are links coming from low-quality websites or web pages, and typically they are unrelated to the topic of your website or web page. Bloggers attempting to artificially enhance their Google ranking (popularity) buy backlinks from scam artists. These spammy backlinks attempt to trick Google into thinking your website or web page is trusted. This tactic might work temporarily, but in the end, spammy backlinks destroy a website's reputation and trust in the search engines. Search engines measure a website’s trust through the type of backlinks it receives.
Social Signals - Recently there has been an explosion of content shared through social network channels - Facebook, Twitter, LinkedIn to name a few. Google looks at links shared through social channels differently than it does backlinks from websites, but social signals do count in the grand scheme of things. There is no doubt that the rising social signals is the new SEO.
For more about backlinks building for blogs and bloggers, check out the articles below: