The Vonage Voice API WebSockets feature has become generally available after leaving beta status. This feature allows for two-way communication over a single persistent TCP connection, simplifying the HTTP response and request cycle. The tutorial covers building a small web server in Ruby to work with WebSockets, handling incoming voice calls, WebSocket connections, and rendering HTML. It requires Ruby 2.7 or higher, several gems, and a Vonage API account with a virtual phone number. The application uses Rack as the web interface and Thin as the web server. The tutorial covers creating a folder structure, defining dependencies, building the server, and creating routes for handling WebSocket connections, serving the index view, returning instructions to the Vonage Voice API, and acknowledging event lifecycle data.