ADO.NET is a set of libraries included in the Microsoft .NET Framework that help you to communicate with various data stores from .NET applications.

The ADO.NET libraries include classes for connecting to a data source, submitting queries, and processing results. You can also use ADO.NET as a robust, hierarchical, disconnected data cache to work with data off line.  

The central disconnected object, the DataSet, allows you to sort, search, filter, store pending changes, and navigates through hierarchical data. 

The DataSet also includes a number of features that bridge the gap between traditional data access and XML development.  Developers can now work with XML data through traditional data access interfaces and vice-versa.