A link campaign is the process of building links to improve the ranking of your site in search engine results.
For example, when you search a keyword on Google, millions of results show up. How does Google decide which result is first and which result is buried on page 50? It has to do with keywords (how directly related your search term is connected to the content of the webpage) and a successful link building campaign.
To achieve SEO (Search Engine Optimization) or, more simply put, a high ranking result from a search engine, you must have external sites linking to yours. There are many ways to accomplish this, not limited to reciprocal links (when two blogs are mutually linked to each other), resource links (almost like a “Further Reading” section of a book), and signatures or blog comments with a hyperlink. The more of these that can be circulated, the more successful your link campaign. And the more successful your link campaign, the more likely your website will show up on search engines like Google, Yahoo!, or Bing.