What is the purpose of using the local-exec provisioner?

The local-exec provisioner invokes a local executable after a resource is created. This invokes a process on the machine running Terraform, not on the resource.

Note that even though the resource will be fully created when the provisioner is run, there is no guarantee that it will be in an operable state - for example, system services such as sshd may not be started yet on compute resources.