Where does the long tail come from? What is long tail and why is it called long tail?

Long tail has become more prominent in this digital area. Internet has changed the whole perspective of doing business. Nowadays, you can find almost everything online. Example, if you want to purchase an album of some unknown Africa musicians or Japanese Acapella music from the record shop like Speedy, HMV or the big time American music retailer like Wal-Mart, you may not find those albums on the shelf in the shop. The reason being is, there is so little demand for those albums and it makes no sense for the record shops to display those albums on the shelf. The shelf space is limited and don’t you think it is better off to display the more popular or the top ten hits on the shelf? The survival of those record shops depending on  the sale  of the albums. So they cannot take the risk to display albums that only sell 1 or 2 copies per year!