Terraform state is a representation of the infrastructure that Terraform manages. Terraform uses state to track the current status of the resources it creates and to plan future changes. However, Terraform state is not aware of any changes made to the resources outside of Terraform, such as through the Azure Cloud Console, the Azure CLI, or the Azure API. Therefore, changing resources via the Azure Cloud Console does not update the current state file, and it may cause inconsistencies or conflicts with Terraform's desired configuration. To avoid this, it is recommended to manage resources exclusively through Terraform or to use the terraform import command to bring existing resources under Terraform's control.
When you change a Terraform-managed resource via the Azure Cloud Console, Terraform does not immediately update the state file to reflect the change. However, the next time you run terraform plan or terraform apply, Terraform will compare the state file with the actual state of the resources in Azure and detect any drifts or differences. Terraform will then update the state file to match the current state of the resources and show you the proposed changes in the execution plan. Depending on the configuration and the change, Terraform may try to undo the change, modify the resource further, or recreate the resource entirely. To avoid unexpected or destructive changes, it is recommended to review the execution plan carefully before applying it or to use the terraform refresh command to update the state file without applying any changes.
Reference = Purpose of Terraform State, Terraform State, Managing State, Importing Infrastructure, [Command: plan], [Command: apply], [Command: refresh]