This is a circular paraboloid, a shape with “one axis of symmetry and no center of symmetry,” according to Wikipedia, which also, helpfully, says a *circular* paraboloid is a paraboloid that contains circles.
There’s an equation — z=(x2/a2)+(y2/b2) — that describes a circular paraboloid if a and b are equal.
It’s a useful shape because a straight line that bounces into a circular paraboloid at any point will want to bounce off toward the same focal point … which means it’s a super-useful shape for things like radar antennas and the magnifying mirrors used in telescopes. It’s also the shape of a wok, which is why Chinese cookware can serve so well as an impromptu wireless signal-booster.
The picture was one of the Featured Images of 2019 on Wikimedia Commons.
