Terraform Structure Overview

A Terraform project usually contains four important blocks:

Now let’s see each one with examples.

🌍 1. Terraform Block

The terraform block is used to configure settings that affect Terraform itself, not the cloud provider or the resources. The terraform block tells Terraform how to behave.

It does not create infrastructure — it configures Terraform’s settings.

You usually place it at the top of your file.

What it does:

• Defines required providers
• Pins provider versions
• Sets Terraform CLI version
• Configures backend (remote state)

Example:

terraform {
  required_version = ">= 1.5.0"

  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 6.0"
    }
  }

  backend "s3" {
    bucket = "my-tf-state-bucket"
    key    = "terraform/state.tfstate"
    region = "ap-south-1"
  }
}

Components Explained:

• required_version Ensures Terraform is using the correct version.
• required_providers Tells Terraform which providers to download and their versions.
• backend Where the state file is stored (local by default, S3/DynamoDB for teams).

🔍 So what happens when you don’t add the block?

Terraform will:

• Automatically install the latest AWS provider version
• Use whatever version it finds suitable

This is okay for learning or small tests, but dangerous for production.

✅ Why Terraform Works Without the terraform Block

1️⃣ Terraform Automatically Downloads the Required Provider

If you write this:

provider "aws" {
  region = "eu-east-1"
}

and Terraform sees that you used:

resource "aws_instance" "web" {}

Terraform automatically understands that you need the AWS provider and downloads the latest compatible version.

So the terraform block is not mandatory.

✅ Then Why Do We Use the terraform { required_providers {} } Block?

👉 This block is used to control versions and source of providers, especially in production.

Example:

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 6.23.0"
    }
  }
}

This ensures:

• Same provider version for everyone (Team members get consistent results)
• Avoids breaking changes (A future Terraform update won’t suddenly break your code)
• Explicit control (You know which version is being used)

☁️ 2. Provider Block (Mandatory)

This tells Terraform which cloud we are using.

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 6.0"
    }
  }
}

provider "aws" {
  region = "ap-south-1"
}

✔ Explanation

• required_providers: Ask Terraform to download AWS provider plugin.
• provider "aws": Sets region and credentials (default uses aws configure).

🚀 3. Resource Block (Creates Infrastructure)

A resource = something Terraform will CREATE, UPDATE, DELETE.

Examples:

• EC2 instance
• VPC
• S3 bucket
• IAM user
• RDS database

Syntax:

resource "<PROVIDER>_<SERVICE>" "<NAME>" {
  # arguments
}

Example:

resource "aws_s3_bucket" "mybucket" {
  bucket = "my-tf-bucket-123"
}