A data mart is a subset of data from an enterprise data warehouse in which the relevance is limited to a specific business unit or group of users.
Data marts provide a long-range view of data within a given subject area, such as sales or finance. Data marts provide the same benefits of a data warehouse, but with limited scope and size.
Data marts are used by a variety of businesspeople. The need for a data mart usually arises because it is too time-consuming to collect the information the users need directly from the source database.
A data mart gives users direct access to specific data about the performance of their business unit. It is a cost-effective alternative to a data warehouse, which can take many months to build. A data mart is easy to use because it is designed specifically for the needs of its users, thus a data mart can accelerate business processes.