The remote backend can work with either a single remote Terraform Cloud workspace, or with multiple similarly-named remote workspaces (like networking-dev and networking-prod). The workspaces block of the backend configuration determines which mode it uses. To use a single remote Terraform Cloud workspace, set workspaces.name to the remote workspace's full name (like networking-prod). To use multiple remote workspaces, set workspaces.prefix to a prefix used in all of the desired remote workspace names. For example, set prefix = "networking-" to use Terraform cloud workspaces with names like networking-dev and networking-prod. This is helpful when mapping multiple Terraform CLI workspaces used in a single Terraform configuration to multiple Terraform Cloud workspaces3. However, one remote backend configuration always maps to a single remote workspace, either by name or by prefix. You cannot use both name and prefix in the same backend configuration, or omit both. Doing so will result in a configuration error3. Reference = [Backend Type: remote]3

The provider for the aws_vpc resource is aws, as the resource type begins with aws_, which denotes that it is managed by the AWS provider.
References:
Terraform Providers

Sensitive values such as API tokens should be stored in a secure way, either in Terraform Cloud variables marked as sensitive or in HashiCorp Vault. Storing secrets in version control systems or plaintext files is not recommended.
Reference:
Terraform Cloud Environment Variables

Explanation
Running terraform fmt without any flags in a directory with Terraform configuration files will not check the formatting of those files without changing their contents, but will actually rewrite them to a canonical format and style. If you want to check the formatting without making changes, you need to use the -check flag.

A provider configuration block is not required in every Terraform configuration. A provider configuration block can be omitted if its contents would otherwise be empty. Terraform assumes an empty default configuration for any provider that is not explicitly configured. However, some providers may require some configuration arguments (such as endpoint URLs or cloud regions) before they can be used. A provider's documentation should list which configuration arguments it expects. For providers distributed on the Terraform Registry, versioned documentation is available on each provider's page, via the "Documentation" link in the provider's header1.
References = [Provider Configuration]1