The terraform init command is used to initialize a working directory containing Terraform configuration files.
This command performs several different initialization steps to prepare the current working directory for use with Terraform, which includes initializing the backend, installing provider plugins, and copying any modules referenced in the configuration. However, it does not validate whether all required variables are present; that is a task performed by terraform plan or terraform apply1.
References = This information can be verified from the official Terraform documentation on the terraform init command provided by HashiCorp Developer1.

Explanation
Terraform validate reports configuration consistency errors, such as declaring a resource identifier more than once. This means that the same resource type and name combination is used for multiple resource blocks, which is not allowed in Terraform. For example, resource "aws_instance" "example" {...} cannot be used more than once in the same configuration. Terraform validate does not report errors related to module versions, state differences, or formatting issues, as these are not relevant for checking the configuration syntax and structure. References = [Validate Configuration], [Resource Syntax]

This command will initialize the new backend and prompt you to migrate the existing state file to the new location4. The other commands are not relevant for this task.

Terraform.tfstate
Explanation:
The name of the default file where Terraform stores the state is terraform.tfstate. This file contains a JSON representation of the current state of the infrastructure managed by Terraform. Terraform uses this file to track the metadata and attributes of the resources, and to plan and apply changes. By default, Terraform stores the state file locally in the same directory as the configuration files, but it can also be configured to store the state remotely in a backend. References = [Terraform State], [State File Format]

Explanation
This is not a valid Terraform collection type, as Terraform only supports three collection types: list, map, and set. A tree is a data structure that consists of nodes with parent-child relationships, which is not supported by Terraform.