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There are two types of export One using the Export function and One using the local HD publish service
First, the Export Function:
On the Export Location section, there is a checkbox labeled {Add to this catalog}. If checked the derivative (export image) is added to the catalog and tracked like any other photo. If unchecked, LR forgets about the exported file and you can do anything you like with the exported file outside of LR. If checked, LR records the path for the image in its catalog and expects the file to be there. If the exported file is renamed, moved or deleted outside of LR, then LR will report it as missing.
Second, the Publish Service:
On the Export Location section, there is no checkbox labeled {Add to this catalog}. So LR does not track the result derivative file. It does track the Source file. And if you make any changes to the source image in LR, LR will mark that file in the Publish Service as needing to republish. Republish will update the file in the destination location. It does dot track the presence of a file in the destination location. So you can rename, move or delete the result derivative file outside of LR without disrupting the order in the catalog.