Inb4: not my area of expertise, but I worked with a company that was providing data on movie rights. The way I understand it is that it's a Cartesian explosion of complexity under the hood. There are at least rights to a version of the movie and the soundtrack/theme song. They can function independently in a region and are granted exclusively or non-exclusively in a region based on timing.

As a bit of a contrived example, you want to distribute Superman 4 in China for a year. You have to secure rights to the film, but you cannot secure rights to the score from the US version as the license is not compatible. You have to get a license-compatible score and make sure the movie complies with the Chinese censorship. And the licensing periods have to overlap.

Multiply that by however many regions you want to distribute the movie in and add accounting complexity for each region.