Explanation
The current implementation of Terraform import can only import resources into the state. It does not generate
configuration. A future version of Terraform will also generate configuration.
Because of this, prior to running terraform import it is necessary to write manually a resource configuration
block for the resource, to which the imported object will be mapped.
While this may seem tedious, it still gives Terraform users an avenue for importing existing resources.
https://www.terraform.io/docs/import/index.html#currently-state-only

Explanation
The terraform refresh command is used to reconcile the state Terraform knows about (via its state file) with
the real-world infrastructure. This can be used to detect any drift from the last-known state, and to update the
state file.
This does not modify infrastructure, but does modify the state file. If the state is changed, this may cause
changes to occur during the next plan or apply.

Explanation
The terraform destroy command terminates resources managed by your Terraform project. This command is
the inverse of terraform apply in that it terminates all the resources specified in your Terraform state. It does
not destroy resources running elsewhere that are not managed by the current Terraform project.
https://learn.hashicorp.com/tutorials/terraform/aws-destroy

Explanation
https://www.terraform.io/language/expressions/version-constraints#-3
Allows only the rightmost version component to increment. For example, to allow new patch releases within a
specific minor release, use the full version number: ~> 1.0.4 will allow installation of 1.0.5 and 1.0.10 but not
1.1.0

Explanation
External Services mode stores the majority of the stateful data used by the instance in an external PostgreSQL
database and an external S3-compatible endpoint or Azure blob storage. There is still critical data stored on the
instance that must be managed with snapshots. Be sure to check the PostgreSQL Requirements for information
that needs to be present for Terraform Enterprise to work. This option is best for users with expertise
managing PostgreSQL or users that have access to managed PostgreSQL offerings like AWS RDS.