Answer
Elliptical cylinder.
See image:
.
Work Step by Step
There is no z in the equation; thus we have a cylinder.
In the xy-plane (z=0), the trace is an ellipse
$\displaystyle \frac{x^{2}}{(1/4)^{2}}+\frac{y^{2}}{(1/2)^{2}}=1$
and likewise in all the planes parallel to $z=0$.
The resulting surface is an elliptical cylinder, with the z-axis as its axis.
