I don’t understand why I should put the pivot of the backgroud to the bottom left of the image and put this pivot at the position (0,0).
It will not be easier to keep the center of the image and the camera at position (0,0)? In this case, if I change the image and the screen size, I do not have to move the camera back to the center of the image.
No significant reason for this, but possibly, for the lectures perspective, counting across from zero upwards in positive numbers rather than having game objects to the right of the 0,0 being in the positive, and those to the left being in the negative? This is just a guess, possibly a bit easier for students approaching Unity/development for the first time etc.