Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
N is just the natural numbers, and A is affine line. It mean $k[N^2]\cong k[x,y]\cong O(A^2)$. It's monoid analog of the Pontryagin duality between Z and $S^1$
