I'm not being able to visualize this region.
I don't have or know any kind of software that can graph this:
$$R = \{(x,y,z) \in \mathbb R^3 \mid (-1 \le y \le 1) \wedge (y^2 \le x \le 1) \wedge (0 \le z \le x) \}.$$
I did a few drawings but I'm not convinced.
Could anyone graph this for me and tell me the used software?

Well, it's hard to visualize because it is -- apparently -- very arbitrary. But I'll try to help:
Your first condition is $y$ between -1 and 1. Imagine two planes, each parallel to the $x-z$ plane, one at $y=-1$ and one at $y=1$.
For your second condition, concentrate on the $x-y$ plane and imagine plotting $x=1$ and $y^2=x$ (or $y=x^{1/2}$). $x$ lies in the area between these two plots. Imagine both plots extended vertically in the $z$ direction. That's your second condition.
Third, imagine a plane that contains the $y$ axis, and everywhere on the plane, $z=x$. Also imagine the $xy$ plane (where $z=0$). The volume between those two planes is your third condition.
The intersection of these volumes is your range.
Hope that helps.