Absolutely nothing (other than the scale of the challenge). Google doesn’t care whether you’re a startup, a major financial institution or the smallest online retailer – all it cares about is connecting people with the most relevant content for each search query. The SEO requirements for a startup are exactly the same as the world’s biggest brands and search engines want to see the same things from you as any other kind of business.
The term “organic traffic” is used for referring to the visitors that land on your website as a result of unpaid (“organic”) search results. Organic traffic is the opposite of paid traffic, which defines the visits generated by paid ads. Visitors who are considered organic find your website after using a search engine like Google or Bing, so they are not “referred” by any other website.