Question 771158
Assuming you mean, like {{{y=(x-2)(x+2)}}}, the "turning point" would be the vertex, either a maximum point or a minimum point.  Your example allows you to quickly find horizontal number line intercepts; the x value for the vertex will be in the exact middle of these horizontal  x intercepts.  


x-intercepts, the "zeros" of y:
{{{(x-2)(x+2)=0}}}
Either x=2 or x=-2
THOSE are the x-intercepts, where y=0, where parabola crosses the x-axis.


What is x at the vertex?
{{{(2+(-2))/2=0}}}
{{{highlight(x=0)}}} is the coordinate for the vertex.


What is y coordinate at the vertex?
{{{y=(0-2)(0+2)}}}
{{{y=(-2)(2)}}}
{{{highlight(y=-4)}}}


MEANING: the vertex of this parabola is (0, -4)