When you freshly install a ScandiPWA app, you will notice many empty directories, such as src/ and public/. This is due to the fact that the original code of ScandiPWA is installed as an npm package, which you can access by going to the node_modules/@scandipwa/scandipwa directory.
With the newly created ScandiPWA app, you can override the original files of the ScandiPWA theme, create extensions, and extend its functionalities.