what is the need of y location here

I don’t know if this answers your question.   This is a 3d animation, so you could move the ball in the y direction if you wanted to.  He only moves it in the x and z direction so you only have to think about those two, but it still needs a value.   If it was a 2d animation then you would only have the two axises.  I frequently forget that there are three axises to think about, since you only see it in 2d.   You should set the y-axis to some other constant besides 0, or set it to a line a see what happens.  Good luck, you are getting to the really fun stuff.