Certain sites contain assignments that are linked to other assignments at remote sites (e.g. point-to-point microwave links, or wide-area simulcast). This is indicated by the 'Links' column in the site information window:
Clicking the number will draw the links on the map with green lines. Clicking one of the green lines (outside the site highlight circle, if it is even shown - it is not in the above image), will cause the map to fly to the remote site and that site's information window will open.
After clicking on the original link line, the remote site is shown. Clicking on its new link line would jump back to the original site.