What is the hidden “_gsdata_” folder that appears in my synced folder?

This folder contains: – Synchronization state file “_file_state._gs” which is required for GoodSync to work properly. – Job logs (*.log files) for all jobs that sync this folder. – Previous versions of files deleted/overwritten by GoodSync are located in “_saved_” subfolder. – Job Tags (*.gst files) that tag the folder per specific job.

This folder has been created from the Goodsync backup program.  You can delete it, but it will be recreated in the folder that is being backed up every time you perform a sync