I’ve written previously about the structure of publishing contracts in terms of what rights you may agree to give to a publisher and what rights you keep for yourself. The rights you keep for yourself—hopefully to sell them later to someone else—are called “retained rights”, i.e., rights you retain for later sale.
This can happen in a number of contexts and for a number of reasons: for example, if you sell print rights in a book to a small publisher that doesn’t (or doesn’t yet) have experience with, or a mechanism for, say, creating audiobooks, you might decide to retain your audio rights and try and sell them separately to an audio publisher like Audible or Tantor.
If you’re working with a publisher that doesn’t have a significant foreign presence or an easy way to exploit your rights in other countries, you may choose to retain your foreign rights and try to sell them to foreign publishers separately. If you have an agent, the agent can negotiate these kinds of transactions and, with any luck, will have a foreign rights sub-agent who can help with the foreign rights sale.
There are some rights that are usually good to retain if you can: for example, film/TV and merchandising rights. While some publishers can exploit these rights, many can’t do a better job than you (or your agent) could do if you choose to sell them to a more targeted entity with more expertise or contacts in the relevant area. If you work with a publisher like Disney, with a big media presence in film/TV, giving them your film/TV rights might make sense, particularly if you can negotiate a price you’re happy with. However, if you’re working with a publisher that doesn’t have a presence in the film/TV area, it can be a good idea to ask your agent about selling those rights separately, through an expert sub-agent in that area.
In terms of what you can retain and what you can’t, a lot of this has to do with bargaining power. If you’re a well known author with a lot of bargaining power—and you may then have a team of agents and lawyers working for you!—you may be able to retain more rights and/or negotiate higher prices if you decide to sell the rights. If you’re in a situation of lesser bargaining power, you may have to take what you get, or decide to try submitting to another publisher.
Sometimes, giving away more rights doesn’t matter in practice. I write a lot of books about American law and I am often asked to give world rights (all countries) to a publisher, rather than retaining foreign rights myself. Generally, this isn’t a problem because my American law books don’t have much of a market in other countries.
In any event, the rights you sell versus the rights you retain is something you should think about—and consult with an agent or attorney if you need to—to make sure you’re negotiating the best deal under the circumstances. You can’t always get exactly what you want, but if you understand your rights you can do your best to make the most effective deal possible.