What is the purpose of a Terraform module?

A Terraform module serves the purpose of abstracting and reusing Terraform configurations. Modules are a fundamental building block in Terraform that allow you to encapsulate a group of resources into a single unit, which can then be reused across different parts of your configurations or in different projects altogether. This promotes modularity and enables developers to write DRY (Don't Repeat Yourself) code, making it easier to maintain and update infrastructure as changes are made.

By using modules, you can define a set of resources once and then call them multiple times, potentially with different parameters, thereby reducing the complexity and improving organization within your infrastructure code. For example, a network configuration module can be written once and used in various environments like development, staging, and production.

In contrast to the other options, the purpose of creating duplicate configurations does not align with best practices, as Terraform encourages modularization rather than repetition. While performance improvements may occur as a secondary effect of better organization, that is not the primary intent of modules. Access control management is typically handled through other Terraform features and tools rather than through the use of modules, which focus primarily on resource organization and reuse.