kevin Said..
ADO.NET is comprised of many classes, but five take center stage:
Connection
Represents a connection to a data source.
Command
Represents a query or a command that is to be executed by a data source.
DataSet
Represents data. The DataSet can be filled either from a data source (using a DataAdapter object) or dynamically.
DataAdapter
Used for filling a DataSet from a data source.
DataReader
Used for fast, efficient, forward-only reading of a data source.