A data warehouse that is designed for a particular line of business, such as sales, marketing, or finance.
In a dependent data mart, the data can be derived from an enterprise-wide data warehouse.
In an independent data mart, data can be collected directly from sources.
– From Oracle Database Data Warehousing Guide 10g R2
A data mart is a collection of data that is optimized for a specialized set of users who have a finite set of questions and reports. For example, a shipping department could use a data mart to analyze how shipping costs are affected by geography and time of year.