What is the Long Tail?

My definition is..

"Make everything available everywhere for everyone and provide tools to find them"

..which means that..

• "..everything..": There are several unpopular products that can be sold to niche markets
  
• "..everywhere for everyone..": Similar niche markets can be found all around the world
  
• "..tools..": The vast amount of products need tools like search engines, suggestions, reviews and so on, to help the consumer find what he really needs

..for instance..

In case of books:

• Amazon claims to sell more than 5,000,000 books
• Any physical store can sell up to 100,000 books
• It is certain that not all of those 5 million books are from the top 100,000 selling books. They are also from the less famous ones, that brick and mortar book stores would not sell at all.
• The sales of those less famous books is nearly the 25% of the whole.

Long tail