Use, Copy or Add, and don't use Move.
It depends on one thing only: Do you copy the photos from the memory card (or connected USB camera) by yourself, using the explorer, or any other file tool, to its final location? If yes, then use Add.
If you would like Lightroom to move the photo to its final location, and at the same time maybe take care of the folders/names and even rename the photo, use Copy.
Just my 0.02: I let LrC do the job. Lr manages my folder structure and renames the photo upon copying it from the memory card, giving it a unique number and date as file name.
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