This subject pops up now and then as I encounter people doing the implementation "thing". I wrote this little piece in March 2009. I've clipped it out and posted it here again:
Language...with Revit's parameter naming the follow is true:
Door Number = "Mark" (not the person but the signature, ID or identifying "mark")
Window "type" = "Type Mark"
Out of the box, Revit's tags are assigned to these as described above. A door number is unique for each door so its tag is using a label assigned to the "Mark" parameter. Windows, for the most part, are defined according to a "type", a common letter or number designation for each window of a given "type" or configuration, therefore a window's tag is assigned to the "Type Mark" parameter.
"Mark" is located in the Element properties dialog while "Type Mark" is located in the Type Properties dialog. Most of Revit elements have both. Some Mark values are automatically supplied based on the "last" value entered and many are not. Type Mark values are not supplied with the assumption that each project will have its own needs and will be defined accordingly.
If you don't approve of the out of the box setting, you can create your own tag so that you can properly identify an element according to your needs.