The web is built on links, and web users routinely use links to find the information they need. When a site links to your site, web users follow those links, resulting in web traffic, or referral traffic. When these backlinks, also called inbound links, come from high quality sites, they also tell Google your content is authoritative and trustworthy. This is important because inbound links from respected sites are an SEO ranking factor, so they can boost organic traffic, too.
The majority of web traffic is driven by the major commercial search engines, Google, Bing, and Yahoo!. Although social media and other types of traffic can generate visits to your website, search engines are the primary method of navigation for most Internet users. This is true whether your site provides content, services, products, information, or just about anything else.