Terraform stacks simplify the management of larger infrastructures across multiple environments. They are a collection of infrastructure resources that are managed together as a single unit using Terraform. Each stack typically represents a specific environment, such as development, staging, or production. Terraform stacks consist of two main pieces: components and deployments. Components make up the infrastructure of an environment, while a deployment is the concretization of an environment. Terraform stacks come with a new type of behavior where Terraform understands certain dependencies between your infrastructure components that require multiple plan and apply operations to complete. The benefits of using Terraform stacks include declarative module management, simplified infrastructure environment management, reduced workspace management overhead, and declarative orchestration of Terraform operations. Terraform stacks are currently in public preview and are only available through HCP Terraform. They are a cost-effective alternative to Terraform Cloud for managing Terraform configurations across multiple environments.