What is an affiliate program?
An affiliate program allows you to earn revenue for referrals that lead to sales (usually, from a webpage or special link). For example, if I sell a book via an Amazon.com link from this website, Amazon's affiliate program pays me a small percentage (between 1-10%, depending on the type of product(s) purchased and the number of referred products shipped in a given month). Peachpit, my publisher, also has an affiliate program that pays a flat 8% of referred sales (my book link at Peachpit). If you have a large audience, you can make quite a bit of money this way, and there are quite a few businesses out there whose primary source of income is affiliate revenue.
Linking to Amazon is easy. For example, if you buy my book through this link, I get a small cut. Here's how I got that link:
All I did to get the link was browse to my book and click on "Short Link To This Page." Once you are active in the Amazon Associates program, that header bar becomes visible. I can also link to things like an Amazon search for "Aerial Photography," or anything else on Amazon.
Peachpit's affiliate program uses Rakuten Linkshare, which is much more complicated and requires wading through the Linkshare interface, but the referral percentage is higher.
Why are you telling me this?
If you are writing about or reviewing Aerial Photography and Videography Using Drones on your website, you can refer people to Amazon and/or Peachpit's website and earn a percentage of sales if someone buys the book. Amazon will actually pay you for everything someone purchased during the browsing session after they click over, so if they clicked over, passed on purchasing my book, but then bought a camera, you'd get a percentage of the camera sale.
Peachpit, who publishes my book, also has an affiliate program, which pays 8% of sales.
Signing up is pretty easy. All you need is a website.
Affiliate programs are great and can generate quite a bit of revenue if you are an influencer and have a large audience. Even if you aren't publishing as a full time career, participating in an affiliate program can help to pay for your hobby, or kickstart you as you try to build a new career. Good luck!