Code in the Terraform language is stored in plain text files with the .tf
file
extension. There is also
a JSON-based variant of the language that is named with
the .tf.json
file extension.
Files containing Terraform code are often called configuration files.
Configuration files must always use UTF-8 encoding, and by convention usually use Unix-style line endings (LF) rather than Windows-style line endings (CRLF), though both are accepted.
A module is a collection of .tf
and/or .tf.json
files kept together in a
directory.
A Terraform module only consists of the top-level configuration files in a directory; nested directories are treated as completely separate modules, and are not automatically included in the configuration.
Terraform evaluates all of the configuration files in a module, effectively treating the entire module as a single document. Separating various blocks into different files is purely for the convenience of readers and maintainers, and has no effect on the module's behavior.
A Terraform module can use module calls to explicitly include other modules into the configuration. These child modules can come from local directories (nested in the parent module's directory, or anywhere else on disk), or from external sources like the Terraform Registry.
Terraform always runs in the context of a single root module. A complete Terraform configuration consists of a root module and the tree of child modules (which includes the modules called by the root module, any modules called by those modules, etc.).