Hi this article http://www.ams.org/notices/200302/what-is.pdf mentioned "$p − q$ in the group of divisor classes $H^{1}(M, O^{∗})$, where $M$ is the elliptic curve and $O^{∗}$ is the sheaf of nonzero holomorphic functions on it."
In the last three years of practicing math I have just been learning divisors are formal sums of the order of a function along a cover or the 1-codimensional subvarieties. I don't know how to write the subvariety or cover in the product of the order yet but I don't see how the zero $p$ and pole $q$ are expected to fit in there.
May I have a brief explanation of the difference between the Weil and Cartier divisor and the divisor class mentioned in the article?