Twilio allows developers to build serverless apps using only TwiML Bins and a few lines of XML, eliminating the need for localtunnel or server setup. With a Twilio account, users can create three simple apps: an SMS forwarding app that forwards incoming calls to another number, a conference line that connects multiple callers, and a Rick Roll app that plays a prank call when a specific number is dialed. These apps can be built using the Twilio Console, where users can select "TwiML Bins" and add code to create their own apps. With just 4 lines of code for SMS forwarding and a few more lines for the conference line and Rick Roll app, developers can start building these apps without any additional setup or downloads.