If UML elements are placed inside a package on a class diagram, they belong to that package. In the model browser these elements are also positioned below the package, indicating their dependency towards the package.
Once an element is taken away from a package in the diagram, it will also be relocated in the model browser. It no longer belongs to that package.
If an element belonging to a package is used in another class diagram or package diagram, it will get a reference to that package to indicate the dependency.
Data type belonging to a package (left), and reuse of the data type in another diagram (right)