I searched and found a lot of photoshop help threads, but no GIMP threads!

I'm trying to figure out to to layer an image on top of another, then erase all of that layer that I don't want, revealing the original picture underneath.

For example, I have a picture of a Yamaha R6 going down a race track. I also have a picture of an empty, curvy mountain road. I want to layer the picture of the R6 onto the picture of the mountain road, then erase everything around the R6 (the racetrack), revealing the picture of the mountain road underneath. So basically, I'm trying to rip the R6 out of one picutre and put it in another.

I looked online for tutorials, but found nothing because I'm not sure what it's called that I'm trying to do.

Epiphone Les Paul Standard
Dunlop Crybaby Wah
Boss DS-1 Distortion
Boss NS-2 Noise Suppressor
Marshall JCM2000 DSL401
Start a new transparant layer on the mountain picture.

Copy the car into that transparancy.

You can then use the magic wand tool to select just the car (or use isometric paths or something). When you have the car selected, go into the select menu, and choose 'inverse'. This will inverse the selection, and will let you erase everything around the car on the top layer.

You may then need to make changes to blend the pictures together, like burning and blurring.
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