How is the "Path Mappings" in remote python interpreter used?

It's the mappings between local project paths and remote paths on the server.

It uses them to match the local files with the same files on the remoter server when you want to run them.
So let's say you have a main.py file locally in the /local/src folder and you upload it to /remote/src on the server.
The path mappings of the interpreter should have /local/src mapped to  /remote/src in order to use them when you run /local/src/main.py file using SSH interpreter.