When the program synchronizes files, it compares the files in Folder 1 and Folder 2 and copies the new-or-updated files to each other.

* Double Sync:   Copy the files from Folder 1 to Folder 2, then copy the files from Folder 2 to Folder 1.

* Single Sync:   Only copy the files from Folder 1 to Folder 2, or only from Folder 2 to Folder 1.

Note:  If Folder 1 and Folder 2 have the same file name, the older file will be replaced with the newer one. .