What are some examples and explanations of the focus strategy?

focus means only segment of the the market – only women between 18-25 yrs unmarried, cost leadership means – they try to have the lowest costs and the cheapest products.
Focus differentiation – when you identify specific needs of your focus group and you try to give something different. Think about mobile phones – they try to differentiate and one has better camera, other is better for music, next is easy in use, some are big for movies etc. They all are mobile phones but each is designed for different group of people who have different needs. – so instead of doing all the same they try to find the segment of the market which would let them gain the advantage.