Which backend does the Terraform CLI use by default?

The Terraform CLI uses the local backend by default, which means that it stores the state file on the local filesystem. This state file is crucial because it keeps track of the resources that Terraform manages, providing a mapping between the configuration and the actual deployment. When you initialize a Terraform project without specifying a backend, it automatically creates or looks for a terraform.tfstate file in the current working directory.

Using the local backend allows users to work with Terraform in a straightforward manner, especially for small projects or when experimenting. However, as projects scale or collaboration becomes necessary, transitioning to a more robust backend, such as remote or cloud backends, becomes common practice. These backends offer additional features like state locking and remote storage, which are not available with the local backend.

Other options like remote, cloud, and shared do not represent the default behavior when first using Terraform, and they require explicit configuration to be utilized. This local backend is a fundamental aspect of how Terraform operates, making it essential to understand for effective usage.