How does something have -1 holes? (Simple look at Topology)
[Maths: Simple introduction to Tpoplogy]
Title is self-explanatory, we're not getting any younger, let's get on with it.
Topology as a field of Maths is interested in trying to break down geometric objects (such as a torus, or as you would call it a doughnut) and constantly deform it. Think of an inflatable tube used for swimming; topologists are interested in the volume inside of the tube, the surface area and how it would be like living on top of the inflatable tube. You know, like one of those old movies about people shrinking down to the size of ants, where it's Ant-Man / Attack on Titan except there aren't really any superheroes in those movies... and you fight off insects while trying to stay alive and return to your normal size.
It's a genuinely fun field of Mathematics to explore. But, it also requires a lot of foreknowledge on many other disciplines of Maths to fully appreciate. So, don't try too hard to understand it. A simple exposure to its existence is good enough.