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  "body": "\n## Summary\n\nSchubert calculus is the computation of intersections of [[Schubert varieties|Z014Q8KPDD]] in [[Grassmannians|CYPA882RB9]] and [[flag varieties|NHRWCQQKTH]].\nIt works in the [[cohomology ring|RDT4785M4D]], or the Chow ring, where the classes of Schubert varieties form a basis.\nThe products of these classes are given by the Pieri rule and by Littlewood–Richardson coefficients.\nIt answers classical questions of [[enumerative geometry|ZPZA1FKZZC]], such as how many lines meet four general lines in space.\n\n## Explanations\n\n### L1 human\n\nHermann Schubert, in the nineteenth century, counted geometric configurations by turning conditions into symbols and multiplying them.\nFor example, \"a line meets a given line\" is one symbol $\\sigma_1$, and four such conditions give $\\sigma_1^4$.\nA set of multiplication rules then turns $\\sigma_1^4$ into $2$ times the symbol of a single line, so the answer is $2$.\nToday these symbols are cohomology classes of Schubert varieties, and the rules are theorems.\n",
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