I love the squarespace website at the end: "Corpse relocation services"

@Feeds again it is a nice video if you already have a clue about the actual topics, but I don't think it does a good job at explaining that to a layman

can verify: I'm totally lost

I have no idea why the circle is equivalent to 0, and the circle is equivalent to the integers

@NathanMerrill just in case you're wondering: it is about the "fundamental groups"

they are basically properties of topological spaces

in this case we are considering all possible closed paths (loops) in a given space and say two of them are equal if you can continuously deform one into another. and on this set we can consider an operation: you add two paths by cutting both open and gluing pairs of ends together.

and you will find a ball has just one class of loops (which is isomorphic to the trivial group), while on a circle you can always add two (positively oriented) paths to get new paths, and this is isomorphic to the integers

puzzle for you: can you find the fundamental group of a torus

or of a figure of 8