The Twilio CLI is a command line tool that allows developers to quickly send SMS messages using TwiML and the Twilio API, with just a few lines of code. To get started, users need to set up their Twilio account, install the Twilio CLI, log in to their account, purchase a Twilio phone number, and then use the command line to create an SMS message. With this tool, developers can save time by sending quick texts without having to pick up their mobile device, and there are many other cool features and examples available on the Twilio documentation site.