This tutorial series covers the use of Nexmo's Voice API with Node-RED to make outbound calls, including text-to-speech (TTS) phone calls. To get started, users need a Vonage API account and a virtual phone number. They also require an API key, secret, and a voice-enabled virtual number. The tutorial guides users through setting up their Node-RED editor, installing the Nexmo nodes, creating a Nexmo application, building a call control object (NCCO), making the outbound call, and optionally receiving events about the progress of the call. Throughout the process, users need to expose their local server to the internet using tools like ngrok if necessary. The tutorial aims to provide a hands-on experience with Nexmo's Voice API and Node-RED for developers.