I am currently studying A. Beauville's article Determinantal Hypersurfaces.
At (3.2), the author discuss about a family of Jacobians:
For $\delta\in\mathbf{Z}$, let $\mathcal{J}_d^\delta\rightarrow |\mathcal{O}_{\mathbb{P}^n}(d) |_{sm}$ be the family of degree-$\delta$ Jacobians: $\mathcal{J}_d^\delta$ parameterizes pairs $(C,L)$ of a smooth plane curve of degree $d$ and a line bundle of degree $\delta$ on $C$. Finally, we denote by $\Theta_d$ the divisor in $\mathcal{J}_d^\delta$ consisting of pairs $(C,L)$ with $H^0(C,L)\neq 0$. It is an ample divisor, so its complement in $\mathcal{J}_d^\delta$ is affine.
I do not understand what exactly is this family of Jacobians. How does the space $\mathcal{J}_d^\delta$ look like and the map onto $|\mathcal{O}_{\mathbb{P}^n}(d) |_{sm}$? Why is that divisor ample?
I only know that a Jacobian variety of a curve $C$ is a torus which can be identified with the space $\textrm{Pic}^0(C)$ of degree-$0$ line bundles.
I would be very grateful if you could explain me this definition or if you would give valuable references.