A Fallback topic is a type of topic in Power Virtual Agents that is used when the bot is unable to understand the customer's request. When a Fallback topic is triggered, it takes over the conversation and presents the customer with a set of options or a message that allows them to get the help they need. This can include options such as requesting to speak with an agent, providing feedback, or getting more information about the bot's capabilities. Fallback topic can be configured to automatically transfer the customer to an agent.
References:
* https://docs.microsoft.com/en-us/power-virtual-agents/create-bot/fallback
* https://docs.microsoft.com/en-us/power-virtual-agents/create-bot/bot-topics