You will create a Swift application that uses the Vapor web framework and the Nexmo Voice API to receive phone calls. To start, you need a Vonage API account with an API Key and API Secret, as well as a virtual phone number purchased through the Nexmo CLI. You'll use Vapor to create a simple web app, add a route for the voice answer, expose your application using ngrok, purchase a Nexmo number, create a Nexmo application to tie everything together, test your application by making a call to your Nexmo number, and learn about Nexmo concepts such as applications, URLs, and NCCO reference.