A lot of statisticians, actuarial mathematicians , reliability engineers, meteorologists, hydrologists, economists. Business and sport analysts deal with order statistics which play an important role in various fields of statistics and its application. This book enables a reader to check his/her level of understanding of the theory of order statistics. We give basic formulae which are more important in the theory and present a lot of examples which illustrate the theoretical statements. For a beginner in order statistics, as well as for graduate students it study our book to have the basic knowledge of the subject. A more advanced reader can use our book to polish his/her knowledge . An upgraded list of bibliography which will help a reader to enrich his/her theoretical knowledge and widen the experience of dealing with ordered observations , is also given in the book.