DataAdapter is a class which is defined is System.Data Namespace which is directly communicates with the central databases it will fetch the data from the databases and fills that data into the datasets

DataAdpter is Bridge between database and dataset/Datatable .

http://vb.net-informations.com/ado.net-dataproviders/ado.net-dataadapter.htm

SqlDataadapter is a interface between database and Ado.Net. dataadapter retrive data from database and fill in datatable using Fill method of dataadapter. For example: datatable _dt=new datatable(); sqlcommand cmd=new sqlcommand(); cmd.commandtype=commandtype.text; cmd.text="select * from tablename"; sqldataadapter ad=new sqldataadapter(cmd); ad.fill(_dt); gdvbind.datasource=_dt; gdvbind.databind();