A data mart is a subject-oriented data repository, similar in structure to the enterprise data warehouse, but holding the data required for the decision support and BI needs of a specific department or group within the organization. A data mart could be constructed solely for the analytical purposes of the specific group, or it could be derived from an existing data warehouse. Data marts are built using a dimensional data model.

There are differences between a data mart and a data warehouse, mostly because of the different natures of the desired results. There is a school of thought that believes that data warehouses are meant for more loosely structured, exploratory analysis whereas data marts are for more formalized reporting and for directed drill-down. Because data marts are centered on the specific goals and decision support needs of a specific department within the company, the amount of data is much smaller, but the concentration is focused on data relevant to that department's operation. This implies that different departments with different analytical or reporting needs may need different kinds of data mart structures (which may account for the diverse set of data mart products on the market).

A data mart is likely to be configured for more generalized reporting for the specific business users within the department. Standard reports are more likely to be generated off of the data mart, which will be much smaller than the data warehouse and will provide better performance.