Actually, let us not underestimate our physical offline sources like print ads (flyers & brochures), business cards, newspaper ads, books or magazines, billboard, by word of mouth that mentions your website or business. Because as we all know, if our Blog or Company Name is already known in public, people will just simply search for you on search engines. And by that, they will reach you.
As far as my personal understanding about URL referrals, getting actual traffic are taken basically from search engines by keyword optimization (SEO) with Luck to be displayed on top of the searched results. Another is through weblogs, link lists from other sites and if you have paid for online advertisements perhaps from banner ads. And perhaps if your Blog is good and you build a frequent readers or subscribers, some people may have bookmarked your URL and visit from time to time to see what’s new. There is also what they call from Email Marketing coming from Bulk email senders used by online marketers and the like. Getting Affiliate links are also a source of referring URLs as well as Social Media that is currently one of the best advertising platform available today. I think these techniques that I mentioned drives visitors to your Web site. I will write more of this soon dissecting every technique in detail.
In a SEO’s point of view, chances are you'll want to know what terms (KEYWORDS) that people have searched for and finding your site on search engines, so you need to analyze that information in a much deeper manner. Those terms/keywords are then used to optimize your website so that your website will be on top on the searched result.