HashiCorp Configuration Language. The structured configuration syntax that serves as the basis for Terraform's configuration language.
HCL establishes the syntax Terraform uses for things like arguments, blocks, literal values, and expressions. But what most people think of as the Terraform language extends beyond just the syntax; the built-in functions, Terraform-specific block types (like resource and variable), and Terraform-specific named values available in expressions are all implementation details of Terraform itself.