Dockerfile COPY commands

I am a bit confused with this command. I am trying to copy a file that is not in the folder I am building the container from.

COPY /file/to/copy .

That is what my argument looks like, but I get an error. Do I have to move all files I want to copy into the container to the folder that I am building from?

COPY can only copy files that are present in the build context.
Usually, this means the folder where the Dockerfile is located and every subfolder and file in it.

Thank you for the clarification!