These get talked about like they're the same thing, which makes sense because they’re both informative audio, but because they serve different purposes they really should be thought of as a different thing entirely. A podcast is built to be found anywhere, by anyone, whenever they want it. An audio tour is built for one specific moment: someone standing in front of something real, wanting more context right now. Those are different uses entirely, and knowing the difference will directly relate to how you build the piece and how successful it is.