Weil divisors = ℤ-combinations of codim-1 subvarieties; Cartier divisors = line bundles modulo trivial. Pic(X) group. Riemann-Roch theorem on curves.
Weil divisors = ℤ-combinations of codim-1 subvarieties; Cartier divisors = line bundles modulo trivial. Pic(X) group. Riemann-Roch theorem on curves.