It's the simplest two-dimensional surface[1] with at least one hole in it. In topology - the math branch that deals with properties of geometric objects and how

It's the simplest two-dimensional surface[1] with at least one hole in it. In topology - the math branch that deals with properties of geometric objects and how they can be deformed - it's one of the two simplest objects, the other being a sphere. (There's a lot of those, too). Donuts ("tori") have the advantage that they're a bit more complex, so they're more interesting, and have interesting properties. Nobody gets much excited by spheres anymore ;) That also means they get a bit more attention. That means you'd expect it to be very common. Not having a lot of donuts would be weird. (Now there's a maxim to live by!) Yes, it's extremely handwavy, and there are probably explanations that are much better and more detailed. Sorry. Best I have. [1] I lie. It's a compact orientable 2-manifold, not a 2D surface. For laymen's terms, I hope the math folks will let me get away with "surface" though.