From Wikipedia

A target market is a group of customers that the business has decided to aim its marketing efforts and ultimately its merchandise. A well-defined target market is the first element to a marketing strategy. The target market and the marketing mix variables of product, place(distribution), promotion and price are the four elements of a marketing mix strategy that determine the success of a product in the marketplace.

Once these distinct customers have been defined, a marketing mix strategy of product, distribution, promotion and price can be built by the business to satisfy the target market