Here you can see a video I produced to practice VFX using After Effects. I took a video of someone pointing at a laptop with a green screen and edited in footage from a previous project of mine - tracking the laptop screen, applying the video footage, keying out the green, using a holdout matte to bring the hand back in over the video footage, and then applying some effects to better blend in the video footage with the laptop and its' surroundings. Here's the final footage, and below that, the original unedited video.
H L Singleton