Terragrunt is an open-source tool that helps manage Terraform configurations by providing additional features and simplifying workflow. It's a popular wrapper around Terraform that addresses common challenges such as keeping configurations DRY, managing remote state, handling multiple environments, and executing custom code before or after running Terraform. Terragrunt provides various useful features like remote state management, DRY configurations, dependency management, configuration inheritance, environment-specific configurations, remote backend configurations, locking mechanism, secrets management, integration with CI/CD pipelines, and configurable hooks. To install Terragrunt, users need to have Terraform installed first, then extract the binary and place it in a directory included in their system's PATH. The top useful features of Terragrunt include remote state management, DRY configurations, dependency management, configuration inheritance, environment-specific configurations, remote backend configurations, locking mechanism, secrets management, integration with CI/CD pipelines, and configurable hooks. Terragrunt relies on a configuration file called terragrunt.hcl that contains settings and parameters that customize its behavior for the project or module. The tool can be used to keep Terraform CLI arguments DRY, share local values centrally, organize infrastructure code into reusable modules, manage multiple modules at once, and enforce code reviews. Best practices for using Terragrunt include creating separate directories for different environments, utilizing remote state storage, standardizing naming conventions, leveraging variable files, using secrets management solutions, specifying version constraints, adopting a GitOps workflow, incorporating Terragrunt into CI/CD pipelines, writing scripts or automation tools to execute Terragrunt commands, and keeping detailed documentation. However, Terragrunt adds complexity and requires education and training for the team. Alternative options include using 'pure' Terraform, Terraspace, or Spacelift, which offer further benefits over Terragrunt.