Project Lists module allows users to create, rename, and delete user-defined lists. All the prepopulated drop downs are known as system lists while user can also create their own list. The default System list is shown below.
Project Admins can create a user defined list (say language list) and add items to the list.
While adding items to the user defined fields, user can add it as a main item or a sub item. They also have access to rename/delete the user defined lists.
System defined lists Cannot be delete or renamed, however new items/sub items can be added to the list.