MathWorld may or not be what you are looking for, but it looks like a good reference site, for short takes on a large number of math topics. Good graphics too.

MathWorld may or not be what you are looking for, but it looks like a good reference site, for short takes on a large number of math topics. Good graphics too. Caveat: only viewed it briefly until now. Last I saw, it was part of Wolfram, though maybe independent earlier. Check the About page for a good overview. https://mathworld.wolfram.com/ https://mathworld.wolfram.com/ https://mathworld.wolfram.com/about/ https://mathworld.wolfram.com/about/