Terraform 0.12 introduces several significant improvements and new features, including first-class expression syntax, a generalized type system, iteration constructs, structural rendering of plans, and context-rich error messages. The new version allows for more flexible and readable configuration files, making it easier to work with data structures such as lists and maps. It also provides improved plan output, showing changes in a form that resembles the configuration language, and includes line-oriented diffs for multiline strings. Additionally, Terraform 0.12 includes enhanced error messages with context-rich details, making it easier to diagnose and resolve issues. The release is available now, and provider developers are encouraged to make their providers compatible with 0.12-ready releases as soon as possible.