A Terraform `variables.tf` file centralizes input variable declarations for a module or configuration. It typically contains multiple variable blocks, each defining a single input variable with its name, type constraint, optional default value, and description. This file serves as a single reference point for all variables used in the configuration, enhancing readability and maintainability. While not mandatory, using `variables.tf` is a common practice to organize and document a module’s expected inputs.

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                                                                                         - [officialParameterize Your Configuration](https://developer.hashicorp.com/terraform/tutorials/configuration-language/variables#parameterize-your-configuration)
                                                                                         - [videoYou should be using tfvars vs variables in Terraform](https://www.youtube.com/watch?v=BHWM4D2GJvI)