Affiliate marketing is the art of marketing products, services or information for others. It doesn't require that you ever house or warehouse a single thing. But it does require that you have an audience to market those things to online. Without that audience, whether it's through search engines like Google or social media channels like Facebook, you'll find a difficult time with affiliate marketing.
SEO should be a core tactic in any marketing strategy. While it might seem difficult to understand at first, as long as you find the right course, book or audiobook, and devote your time to learning, you'll be in good shape. Considering that there are over 200+ ranking factors in Google's current algorithms, learning, digesting and successfully implementing good SEO tactics is essential to the success of your website or blog.
Facebook pages are far more detailed than Twitter accounts. They allow a product to provide videos, photos, longer descriptions, and testimonials where followers can comment on the product pages for others to see. Facebook can link back to the product's Twitter page, as well as send out event reminders. As of May 2015, 93% of businesses marketers use Facebook to promote their brand. A study from 2011 attributed 84% of "engagement" or clicks and likes that link back to Facebook advertising. By 2014, Facebook had restricted the content published from business and brand pages. Adjustments in Facebook algorithms have reduced the audience for non-paying business pages (that have at least 500,000 "Likes") from 16% in 2012 down to 2% in February 2014. 
Inbound marketing refers to a marketing methodology wherein you attract, engage, and delight customers at every stage of the buyer's journey. You can use every digital marketing tactic listed above, throughout an inbound marketing strategy, to create a customer experience that works with the customer, not against them. Here are some classic examples of inbound marketing versus traditional marketing: