SMS messages with Twilio using Crystal` is a tutorial on how to send SMS messages using the `Twilio` API and Crystal programming language. The tutorial starts by introducing the Crystal project, its goals, and syntax, which are similar to Ruby's but faster. It then guides readers through installing the Crystal compiler, setting up a Twilio account, and making HTTP requests to the Twilio API using Crystal. The tutorial concludes by showcasing improved JSON parsing in Crystal.