This help book on ADO give a general overview of the concepts a developer will need if they plan to use ADO as a data access method.

“Microsoft ActiveX Data Objects (ADO) enable your client applications to access and manipulate data from a variety of sources through an OLE DB provider. Its primary benefits are ease of use, high speed, low memory overhead, and a small disk footprint. ADO supports key features for building client/server and Web-based applications.”  (Microsoft / MSDN)