Haskell is a functional programming language that allows developers to write clean, concise, and expressive code. It can be used for various purposes, including sending SMS messages using the Twilio API. To start with Haskell, one needs to set up the developer environment by configuring package managers, installing Haskell, and choosing an Integrated Development Environment (IDE). The popular package manager Stack is preferred due to its isolated and reproducible build system. With Stack, developers can create new projects, install packages, and send SMS messages using Twilio. The language also supports creating "Hello, World" programs in both interactive mode and from a Haskell file.