This has been a very long discussion. I want to put it in simple terms:
First, there are two strategy here, choose one door then switch or choose one door then stay.
If you want to switch then you want your first choice to be the goat therefore you got 2/3 probability that your first choice will be the goat.
On the other hand, if you want to stay then you want your first choice to be the car therefore you got 1/3 probability that your first choice will be the car.

And one more thing for those counting the possible outcomes, you can't distinguish the 2 goats from each other even if they have different colors because it's just either you win or you loose. In the 3 doors, 1 door is the prize and the other 2 doors are nothing.