Data Mart in Data Warehousing

Data Mart in Data Warehousing is nothing else but logical part of data warehouse that can function as standalone specialized datawarehouse.

Wikipedia excerpt:

“A data mart is a repository of data gathered from operational data and other sources that is designed to serve a particular community of knowledge workers. In scope, the data may derive from an enterprise-wide database or data warehouse or be more specialized. The emphasis of a data mart is on meeting the specific demands of a particular group of knowledge users in terms of analysis, content, presentation.”

source: http://en.wikipedia.org/wiki/Data_mart

Consider Data Mart as a small specialised Data Warehouse or independant unit (financial data mart, customer data mart, sales relation, customer support, technical data and similar) in Data Warehouse scheme.