Sentinel is an embedded policy-as-code framework integrated with the HashiCorp Enterprise products. It enables fine-grained, logic-based policy decisions, and can be extended to use information from external sources.
Using Sentinel with Terraform Cloud involves:
* Defining the policies - Policies are defined using the policy language with imports for parsing the Terraform plan, state and configuration.
* Managing policies for organizations - Users with permission to manage policies can add policies to their organization by configuring VCS integration or uploading policy sets through the API. They also define which workspaces the policy sets are checked against during runs. (More about permissions.)
* Enforcing policy checks on runs - Policies are checked when a run is performed, after the terraform plan but before it can be confirmed or the terraform apply is executed.
* Mocking Sentinel Terraform data - Terraform Cloud provides the ability to generate mock data for any run within a workspace. This data can be used with the Sentinel CLI to test policies before deployment.
https://www.terraform.io/docs/cloud/sentinel/index.html

Explanation
terraform init command is used to initialize a working directory containing Terraform configuration files.
Reference: https://www.terraform.io/docs/cli/commands/init.html

Explanation
Check resource addressing
https://www.terraform.io/docs/internals/resource-addressing.html