Porter To The Rescue

He explained the results in Competitive Strategy, which quickly became the bestselling business book ever up to that time. Every company, he said, is subject to five forces: the competitors it currently faces, the threat of new competitors, the threat of substitutes for its products or services, the bargaining power of its suppliers, and the bargaining power of its customers. Within that environment, every company must choose a strategy, and there are only three: achieving the lowest costs, differentiating its products and services, and dominating a niche.
Trying to do some of each -- getting "caught in the middle" -- prevents a company from realizing the benefits of any of these strategies, and as a result it will lose to competitors who choose just one.

http://management.fortune.cnn.com/2012/10/15/michael-porter/?iid=SF_F_Ri
ver