With any of the Marker tools, you can opt to place a source marker. A source marker creates a new viewpoint (e.g. a Section, Elevation, Worksheet, Detail) involving the model as their source.
Any of the Markers – except Interior Elevation – can optionally be defined as a linked marker. Such markers have no model source and do not generate a new viewpoint. Instead, they are placed in the project, then linked by the user to an existing viewpoint, view or drawing. This information is displayed in the marker, which can be used to navigate to the referred item.
An unlinked marker has no model source and displays no linked information. You cannot use it to navigate among markers, but you can define any custom text for it.