What is Data Warehousing?
Data Warehousing is a process for collecting, storing, and delivering decision-support data for some or all of an enterprise. Data warehousing is a broad subject that is described point by point in this Refcard. A data warehouse is one of the artifacts created in the data warehousing process.
William (Bill) H. Inmon has provided an alternate and useful definition of a data warehouse: "A subject-oriented, integrated, time-variant, and nonvolatile collection of data in support of management's decision-making process."
As a total architecture , data warehousing involves people, processes, and technologies to achieve the goal of providing decision-support data that is consistent, integrated, standardized, and easy to understand.
See the book The Analytical Puzzle: Profitable Data Warehousing, Business Intelligence and Analytics (ISBN 978-1935504207) for details.
What a Data Warehouse is and is Not
A data warehouse is a database whose data includes a copy of operational data. This data is often obtained from multiple data sources and is useful for strategic decision making. It does not, however, contain original data.
"Data warehouse," by the way, is not another name for "database." Some people incorrectly use the term "data warehouse" as if it's a generic name for a database. A data warehouse does not only consist of historic data, it can be made up of analytics and reporting data, too. Transactional data that is managed in application data stores will not reside in a data warehouse.