The Link to source provides the same information as that shown under Field locations in the Palette. The difference is that if the selected field is a "grabbed field" it can be reclassified e.g. from local to linked or from linked to local.
The selected field which gave rise to this portion of the Inspector's Attributes view was the City field which was brought into the Template as a "grabbed field" from the Names table. The Link to source (the source is always a Global table) information tells you that the City field is a local field in the City table, a hierarchical link in the License table, and a direct link in the Names table.
Linked fields explained
Help for other Attributes components:
Show in TX Audit Control (Subledger Templates only)
Table of Contents
Global Template - Topics of Interest
Subledger Template - Topics of Interest