Well, a Riemann surface is a certain kind of Hausdorff space. You know what a Hausdorff space is, don’t you? Its also compact, ok. I guess it is also a manifold. Surely you know what a manifold is. Now let me tell you one non-trivial theorem, the Riemann–Roch Theorem.— Gian-Carlo Rota’s recollection of Lefschetz lecturing in the 1940’s, quoted in A Beautiful Mind by Sylvia Nasar.
Read more: Britanica.com
You may also like ti read this: Corona Virus, No Facebook and I Am Stuck at Home