Answer
The set $r=2$ and $z=3$ is a disk of radius $2$ at the height of $z=3$.
Work Step by Step
In cylindrical coordinates, $r$ is always the distance back to the $z$-axis. Thus, $r=2$ corresponds to a circle of radius $2$. Since the $z$-coordinate is the same as in rectangular coordinates, $z=3$ corresponds to the plane of equation $z=3$. Hence, $r=2$ and $z=3$ is a disk of radius $2$ at the height of $z=3$.
