It was such a broad question, you'd have to ask the interviewer what, specifically, was meant by it, because it could mean any one (or more) of what you've suggested, or something else.
Is the program well-written? Poorly-written? Unknown as no-one has looked at it yet? Batch? Database? "Back" or "middle" from e-commerce? What? Are any sub-programs, or calling programs to be considered?
You are "allowed" to ask questions back. Sometimes the reason for an interviewer asking a broad question is to see if you can do that in a reasonable manner.
It is possible to look at any program and "analyse" it in its own terms, but the results will likely be much less useful than if the purpose is known.