Whole concept of jdbc is to provide one unified interface for handling the data base calls.
But with others,we need to provide some configuration information . that may in datasource.xml(In case of J2ee) or in the java code where we trying to load a driver using Class.forName() using DriverManager Approach
It delegates the responsibilities to the vendor specific driver, which will provide the implementation for Interfaces such as Statement etc.
Hope this answered u r Query.
Cheers