Here are the different types of multi-container pod patterns:
A pod spec which runs the main container and a helper container that does some utility work, but that is not necessarily needed for the main container to work.
The adapter container will inspect the contents of the app's file, does some kind of restructuring and reformat it, and write the correctly formatted output to the location.
It connects containers with the outside world. It is a proxy that allows other containers to connect to a port on localhost.