“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.
Search engines are unique in that they provide targeted traffic—people looking for what you offer. Search engines are the roadways that make this happen. If search engines cannot find your site, or add your content to their databases, you miss out on incredible opportunities to drive traffic to your site.
Search queries—the words that users type into the search box—carry extraordinary value. Experience has shown that search engine traffic can make (or break) an organization’s success. Targeted traffic to a website can provide publicity, revenue, and exposure like no other channel of marketing. Investing in SEO can have an exceptional rate of return compared to other types of marketing and promotion.”
Excerpt from: https://moz.com/beginners-guide-to-seo