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

a temporary files when doing the integratin test.
developers use stubs and drivers for time being to conduct 
the test.
after the original modules are developed these will be 
replaced with the actual one.
for the base modules replacement they use drivers and 
for the core modules replacement they use stubs.