If a module declares a variable with a default, what is true about that variable?

When a module declares a variable with a default value, it becomes optional for users of the module to provide a value for that variable. This means that if the user does not specify a value when calling the module, Terraform will automatically use the default value defined within the module. Therefore, the variable does not need to be defined within the module again, as the default provides a fallback value.

This feature enhances the usability of the module by allowing flexibility in configuration, enabling users to override the default only if they choose to specify a different value. It also keeps module definitions clean and succinct, as the presence of a default value means the user can rely on that value when necessary, without any additional requirement to define it explicitly in their module call.