"short tail" long tail"

The terms "short tail" and "long tail" refer to very few products with very high popularity ("short tail") or a lot of products that each one of them is not popular but put together they sell a lot ("long tail"). There are types of businesses in which it makes a lot of sense to serve the long tail (that's how Amazon makes so much money, or at least it was like that when they started), but in others id doesn't -- I guess the telecom industry is a good example for that.

There's a good explanation about this on Wikipedia, look for the "Competition and the Long Tail" part.

A better contrast example between businesses that focus on the short tail vs. the long tail would be traditional Media companies like News Corp and New-media companies like demand media co-founded by richard rosenblatt .  Companies that go after the most popluar items target the short tail, and companies that target huge goups of things are targeting the long tail.