FTC Disclosure: Genealogy.com has an affiliate program. An affiliation is a relation in which merchants pay commissions on sales for links. Clicking on an affiliate link sets a tracking id. If a sale takes place; the merchant might pay a commission on the sale. I use such money to host and develop this site.
NOTE: Browsing in privacy mode strips the id. Ad blocking software strips the id. Some "browser helper objects" replace my id with their id. Ids often magically disappear between the click and sale. You can also "google" the company name which will credit the sale to Google.