ADODB ("ActiveX Data Objects Databases," abbreviated ADO) is the successor of DAO. DAO was actually designed only to be employed with Jet-Databases like Access or Excel. Other databases "must" be connected through ODBC which operates more laboriously and hence more slowly. ADO supports itself however on the OLEDB driver which the ODBC driver unhitches.
OLEDB offers more performance and often more possibilities for the developer. Over ADO, acccess to almost all commonly used databses is available-regardless as to whether or not it is Access, SQL-Server, Oracle, Informix and many more. ODBC connections allow themselves to be used hassle-free as well. However, they are actually superfluous through OLEDB.