Terraform input variables are parameters for modules, declared using variable blocks. They support multiple data types, default values, and descriptions. Users provide values when invoking modules or running Terraform. Accessed via `var.<name>` syntax, input variables enable flexible, reusable infrastructure templates adaptable to various deployment scenarios. They can be marked sensitive for security and are typically defined in a `variables.tf` file.

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                                                                           - [officialDefine Input Variables](https://developer.hashicorp.com/terraform/tutorials/aws-get-started/aws-variables)
                                                                           - [articleTerraform Input and Output Variables Explained](https://kodekloud.com/blog/terraform-variables-explained/)
                                                                           - [videoTerraform Basics: Input Variables](https://www.youtube.com/watch%3Fv%3D2f65JhfYmIo)