The long tail is a frequency distribution pattern in which occurences are most densely clustered close to the Y-axis and the distribution curve tapers along the X-axis. The long tail refers to the low-frequency population displayed in the right-hand portion of the graph, represented by a gradually sloping distribution curve that becomes asymptotic to the x-axis. In most applications, the number of events in the tail is greater than the number of events in the high frequency area, simply because the tail is long.
Wired Magazine editor Chris Anderson popularized the term and applied it to business models of online retailers, content providers and other elements of popular culture. Anderson introduced the concept through speeches and articles in Wired and eventually expanded upon it in a book, "The Long Tail: Why the Future of Business is Selling Less of More," in 2006.
To use concrete examples, Amazon.com and Netflix.com both earn a larger percentage of their profits from relatively obscure, niche books and movies (low frequency events) than from rentals and purchases of best sellers and blockbusters (high frequency events). This same model may be applied to user-generated content sites, like Wikipedia, or the tens of millions of blogs in the blogosphere , where content that caters to hyperfocused topics generate cumulative levels of traffic greater than that for the top 100 blogs.