add note for normal vs. RAG demo

README.md

@@ -8,6 +8,16 @@ Uses OpenAI ChatGPT to generate advice for a given destination.
 
 ![title](screenshot.png)
 
+## "Standard" Version vs. "RAG" Version
+
+This demo is available in two flavours.
+
+The "standard" demo uses OpenAI's ChatGPT (coupled with an on-cluster Weaviate cache) to look up destination advice for any destination.
+
+The "RAG" version (available on the `rag` branch) will **only** produce destination advice for places the system has explicitly been trained on (the files in the [destinations folder on the `rag` branch](https://github.com/dynatrace-perfclinics/traveladvisor/tree/rag/destinations)). Namely, `Bali` and `Sydney`.
+
+The RAG version of the demo mimicks training an LLM on an internal knowledgebase.
+
 ## ⚠️ OpenAI Paid Account Required
 
 You need an OpenAI account with credit added to run this demo!