Framework assemblies are those that are part of the .NET framework and should already be in the global assembly cache (GAC) for any given machine. By identifying those assemblies within the <frameworkAssemblies> element, a package can ensure that required references are added to a project in the event that the project doesn't have such references already. Such assemblies, of course, are not included in a package directly.

The <frameworkAssemblies> element contains zero Or more <frameworkAssembly> elements