On the fortith day, I learned the following things about Terraform.

Terraform .tfstate file and destroy Command

After the creating the terraform.tf file and creating a repository on GitHub, two more files will created after that. Those files are terraform.tfstate and terraform.tfstate.backup.
Open the terraform.tfstate file and it will show you all the resources that you have created in terraform.tf file.
If you want to create another repository, you can add it in the terraform.tf file.
After adding the second repository code in the file, type terraform plan command. It will show the new repository resources to be added.
Write terraform apply --auto-approve command. Auto approve won't ask you YES or NO option everytime and it will make the second repository without making changes in the first one.
Open the terraform.tfstate file and it will show you the first repository resources and the second repository resources that you have created.
Open the terraform.tfstate.backup and it will show you the backup of the earlier resources that you have created.
Tip: Don't try to manually change the .tfstate file.

Terraform Destroy

If you want to destroy the resources, you can do it by writing, terraform destroy. It will destroy all the resources and the repositories that you have created.
If you want to destroy a specific resource, you can do this by simply writing terraform destroy --target github_repository.terraform-second-repo.
If you write terraform plan, it will show you the resources of the second repository that needs to be added.

Before showing you how to validate the terraform, let's make some changes in the terraform files.
Open the terraform.tf file, copy the provider and paste into the provider.tf file.
Remove the token from the provider.tf file and write the following data into it.
```
provider "github" {
    token = "${var.token}"
}
```
Make a variable.tf file and write the following data into it.
```
variable token {}
```
Make a terraform.tfvars file and write the token inside it.
```
token="<token>"
```
After making these changes, type terraform validate command and it will give you the message Success! The configuration is valid.
Now you can destroy and apply the configuration file.

Here you can get an explanation in a video. 40/60 Day of DevOps Challenge