Using the tagInfoList that is output from Get Tagged Linked Element Id this node will output lists useful for obtaining the actual elements that are tagged, including a Link Actual Elements output. These elements can be directly queried for parameter values and similar. It also reports if a given IndependentTag is not tagging a linked element, as shown in the not a Linked Tag output.
In Revit, Tags may reference elements in the current Document, or they may reference an element in a Linked document. There are a number of useful properties that can be obtained from a Tag that references a Linked document. This node returns a list with sublists which include the source element Id, and information needed to determine which document the element resides in.