ngrok` is a universal gateway used by 80% of the Cloud 100 to expose local services, including WebSockets, to public APIs or services like Twilio. `ngrok` operates as an API-gateway-in-development, tunneling traffic from Twilio's Media Stream API to a local web server. The example demonstrates how to set up secure WebSockets with `ngrok` and Twilio's Media Stream API for development and testing, using OpenAI for transcription and summarization. `ngrok` provides an easy way to expose local services to public APIs or services, speeding up the development process, and is a key tool in exposing local services to public webhooks and APIs.