The long tail consists on focusing the efforts of seo for a website in many different keywords to get top positions in Google and not devote all our efforts on a couple of keywords with a large competition.
As explained above the Amazon online store gets most of its profits from the sale of many different books, specialized or minority and not the popular bestsellers.
When we manage the seo of an online store or ecommerce, it is common that the client ask for being positioned for terms like "wine shop" or "white wine", ie, by the name of the industry or sector terms. However, a good seo campaign should focus on promoting individual products. Get good results for each product individually will, no doubt, give you better results; specially because these keywords generate a higher conversion rate and sales.
Consider a practical case. A user looking to buy a red wine Catena. If you search for "red wine" into Google, you get 7240000 results, but not until the end of the first page you will find the first online store offering red wine, which happens to not have this brand, result: 1 visit, 1 bounce, 0 conversion. However, you probably search for what you really want, "Catena wine" in that case you will get 150,000 results and the first store to appear will be to our client and, when clicked, takes you straight to the page of the wine to buy. Results: 1 visit, 1 conversion, 0 bounce. If we multiply these results by many wines get a high number of sales.
In summary, the key to the seo of online stores is the long tail, focus on specific products and not waste efforts on words too generic. An indicator of whether we are making the correct positioning of an online store is the rate of bounce or "bounce rate" is one that shows just how many users have visited a page on our website and are gone in seconds.