This is an online tool to view S2 Cell tokens. To learn more about S2 geometry, see: s2geometry.io. Also check Useful S2 Geometry Links.
There used to exist a very similar tool hosted at s2.sidewalklabs.com/regioncoverer/ but it is long gone now. I came across Wasm with Go to build an S2 cover map viewer by Fabrice AkHeN which combines S2 Cell lib in Go and Wasm which can be seen at s2.inair.space and tweaked it a bit.