Search engines give more priority to websites that have links from other websites based around the same topic and located within the flow of information. This process helps to make your website an authority on the topic and a place for people seeking information to visit. Link building is not an overnight process and should be an ongoing part of your business.
The more quality contextual links your website has, the better position your website will get in the search engines and will then attract more visitors. Everyone knows that more visitors equals more sales.