Think of a DataSet as a local in-memory copy of a set of database tables and their associated relationships and constraints. With the client-server model in the past, client applications held onto a connection to the data source and updated and added records at will. With ADO.NET the DataSet presents a disconnected model. Data, as well as data changes, are contained in the DataSet with no physical connection to the data source.

Changes to a disconnected DataSet can be reconciled against any data source at any time.

A Dataset is not limited to database tables. It can work with XML or for that matter any other data.

George Shepherd, Syncfusion, and Stuart Celarier, Fern Creek