Answer
Circle with equation $y^2+z^2=1$ in $yz$ plane.
Work Step by Step
Here, the points are the intersection between the equation of cylinder $y^2+z^2=1$ and the plane $x=0$.
The set of points that satisfies such equations has the equation of a circle lying in the $zy$ plane, centered at origin $O$, having a circle of radius $1$.
