Data Warehouse is a computer system that keeps organization data. Since sectors names until operational data. For example, in a university system, the data warehouse provides classes informations (avaliations, students, professors), it is the operational level of any university.
Data Warehouse is the way to provide the Business Inteligence (BI). In this case, the system is used to extract useful informations about the business management. It is done through strategically organized data analysis. This is the major difference between a conventional information system and a data warehouse: the information structure. It must be organized to make queries easily and extract useful information. And it is desirable that information structure is extensible (to follow business changes). One example related to universitary context: the Data Warehouse may present statistical graphics about disciplines with highest number of failures. It helps administration of each departament to allocate more professors to that disciplinas.