[HELP] COPY command

I'm fairly new to docker and I have a question about the COPY command.

1 – Does it copy content to inside the image? I mean, would I still need to deploy my app folder to cloud even if the image copied the folder app? (I know an image is used to create containers, my question is if they hold user data in this manner & I know it's possible to save data on docker, but I'm not talking here about this method).

2 – After create an image where I copy an empty folder X and later, before I create a container with this image, I add content to the folder X. The image will be able to copy the new content from folder X to the container? Or it will be needed to recreate the image?

Hope some good soul can help me! Thanks in advance!

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