ADO/RDO

ADO---activex data objects
RDO---remote data objects


ADO acts as a layer between programming languages and OLEDB
RDO acts as a layer between programming languages and ODBC

OLEDB is a successor of ODBC
ODBC---Object Database Connectivity---provides an API methods for using DBMS
OLEDB---Object Liking and Embedding Database----provides API methods for using relational as well as unrelational databases that do no implement SQL