What concept allows Terraform to integrate variables and resource attributes together?

Local values in Terraform enable the integration of variables and resource attributes by providing a way to assign a name to an expression, which can then be reused throughout the Terraform configuration. This ability to define local values helps in simplifying complex expressions and allows for better readability and maintainability of the code.

When you define a local value, it can reference variables and resource attributes, creating a cohesive link between them. For example, you might use local values to compute derived values from variables or to extract specific attributes from resources, thereby creating a smooth integration of different components in your Terraform scripts.

While HashiCorp Configuration Language (HCL) provides the syntax for expressing these definitions, and modules help in organizing code into reusable components, local values specifically focus on the capability to aggregate and streamline variable and resource information. Providers enable interactions with specific services or APIs but do not directly facilitate the integration of variables and attributes like local values do.