T4 is a text templating engine that is used to generate source code and other text-based artifacts from templates. It is a core feature of Visual Studio but requires additional third party tooling for a full-featured experience. Alternatives to T4 include CodeDOM, CodeSmith, and NVelocity, each with their own advantages and disadvantages for different scenarios. Learning T4 involves using the free tools from Tangible and the T4 Toolkit as well as searching online documentation and tutorials.