stub testing: 
In top down approach,a core module is developed.to test 
that core module, small dummy modules r used.so stubs r 
small dummy modules that test the core module.

Driver testing:
in bottom up approach, small modules r developed.to test 
them a dummy core module called driver is developed.

These are the different types of integration techniques

Stub: When u approached top down approach you have to use 
stubs. ie when testing the module from top level hierachy 
to bottom level hierachy
DEF: Stub is nothing but a calling function for the 
function to be tested.

Driver: When u approached bottom up approach you have to 
use driver. ie when testing the module from bottom level 
hierachy to the top level hierachy
Driver: Driver will act as a dummy program for the fucntion 
to be tested

Driver: test tool that replaces a component that takes care 
of the control or the calling of a component or system
Stub:  special purpose implementation of a software 
component that calls or is otherwise dependent on it . it 
replaces a called component