OLE DB is a new low-level interface that introduces a "universal" data access paradigm. That is, OLE DB is not restricted to ISAM, Jet, or even relational data sources, but is capable of dealing with any type of data regardless of its format or storage method. In practice, this versatility means you can access data that resides in an Excel spreadsheet, text files, or even on a mail server such as Microsoft Exchange.
In Visual Basic 6.0, you leverage the flexibility of OLE DB through ADO, the programmer interface to OLE DB. You can even create your own OLE DB Providers in Visual Basic.
OLE DB is not designed to be accessed directly from Visual Basic due to its complex interfaces. Instead ActiveX Data Objects (ADO) encapsulates and exposes virtually all of OLE DB’s functionality.
Visual Basic does allow you to create your own OLE DB Provider by setting the DataSourceBehavior property to vbOLEDBProvider in an ActiveX DLL project. (See Creating the MyOSPObject Class.) By doing so, the OnDataConnection event becomes available to provide notification a connection has been made. For more information, see DataSourceBehavior property.
For More Information For more background on OLE DB see Microsoft OLE DB Overview.