is a term used to refer to various licensing plans that enable copyright holders to grant certain rights to the work while retaining other rights.

Copyleft.

Explanation:

As the exercise explains, copyleft is a term used to refer to various licensing plans that enable copyright holders to grant certain rights to the work while retaining other rights. In other words, copyleft is a term distinct from copyright, the first being an authorization of sorts to people to be able to distribute the work, with certain permission to modify some parts of it or not.