Stubs and Drivers are the small programs used in the integration testing such that these programs are placed where the output of undeveloped modules. that is in some cases, some of the non priority module's output is needed in the project. then to get out of that situation, we write a small program such that it generates exactly similar output of the un-generated module. these programs are called stubs and drivers.
Here stub is used when we are testing the application in top-down approach.
and driver is used when we are testing the application in bottom-top approach.