Links
Links also known as backlinks, hyperlinks, are incoming links to a website or web page.

Link popularity
Improve your rank in search engines by increasing the number of links pointing to your site from high-quality sites by using one-way links and two-way links, these links count toward your link popularity.

Link building
Developing links can be time-intensive, confusing, and frustrating. However it can be one of the single best ways to boost your site's PR (page rank). Websites often employ various techniques to increase the number of backlinks pointing to their website. Some methods like linkbaiting requires quite a bit of planning and marketing to work. When "linkbait" happens, many websites will link to the 'baiting' website because there is information there that is of extreme interest to a large number of people.

Search engine rankings
Search engines use the number of backlinks that a website has as an important factor for determining a website's ranking, popularity, and importance. There are several factors that determine the value of a backlink. Backlinks from authoritative sites on a given keywords, keyword phrase, or topic are more valuable. If both sites have content geared toward the keyword topic, the backlink is considered relevant and believed to have strong influence on the search engine rankings of the webpage. A backlink represents a favorable 'editorial vote' for the receiving webpage from another sending webpage. Another important factor is the anchor text of the backlink. Anchor text is the descriptive labeling of the hyperlink as it appears on a webpage. Search engine bots examine the anchor text to evaluate how relevant it is to the content on a webpage. Anchor text and webpage content are highly weighted in search engine results page (SERP) rankings of a webpage with respect to any given keyword query.

PageRank
PageRank is a link analysis algorithm, named after Larry Page used by the Google Internet search engine that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of "measuring" its relative importance within the set. The algorithm may be applied to any collection of entities with reciprocal quotations and references.

The future of links
Link building is still going to be a strong SEO tool for the foreseeable future. We don't believe that search engine algorithms will place less importance on link popularity for the near future. Links are still the basic connection, the basic relationship, on the Web. Links are going to still be the easiest way for a computer program to judge how relevant and trustworthy a Web page is.

Linking mistakes
A common mistake that many websites make is to link to only their home page and using the same anchor text. The search engines may reduce the value of the links. Varying the anchor text and having links point to other pages of your site. Do not duplicate content on your site. It should also be noted that building too many Backlinks over too short a period of time can get a website's ranking penalized, or de-indexed. Anything above a couple of hundred links a day is considered dangerous.