AD0.NET consists of two fundamental components:
The DataSet, which is disconnected from the data source and does not need to know where the data that it holds is retrieved from.
The .net data provider, which allows you to connect your application to the data source and execute the SQL commands against it.
The data provider contains the Connection, Command, DataReader, and DataAdapter objects. The Connection object provides connectivity to the database. The Command object provides access to database commands to retrieve and manipulate data in a database. The DataReader object retrieves data from the database in the readonly and forward-only mode. The DataAdapter object uses Command objects to execute SQL commands. The DataAdapter object loads the DataSet object with data and also updates changes that you have made to the data in the DataSet object back to the database.