Terragrunt is a lightweight wrapper around Terraform that helps platform teams reuse shared configuration and manage infrastructure across multiple environments without duplicating code. It works by adding a small terragrunt.hcl file per environment that can inherit common settings such as remote state (where Terraform stores its state file), provider configuration, and input variables; Terragrunt then renders the final inputs and runs Terraform commands in the right directories, including orchestrating apply and plan across a stack.
With Terragrunt, shared defaults and environment conventions stay consistent and updates roll out predictably across many modules, while without it teams often copy and edit Terraform blocks per environment, which increases drift, inconsistent state handling, and upgrade risk. This gap exists because Terraform modules promote reuse of resources, but they do not natively enforce inheritance of operational settings across large, multi-environment layouts.