What is the difference between these options...

In the options for "Do the following to the matched file or folder", you can select:
"If file exists: do not copy the file"
and also tick a box that says "Do not copy if a duplicate".
What is the difference?
Thanks
M
"If file exists: do not copy the file"
and also tick a box that says "Do not copy if a duplicate".
What is the difference?
Thanks
M