What is Terraform? Everything You Need to Know | Harness Glossary

Terraform is one of the most popular tools in the modern DevOps toolkit. If you've ever wondered how large teams automate infrastructure provisioning or how you can deploy cloud environments using just code, you're in the right place.

This guide will walk through what Terraform is, how it works, when to use it, how it compares to other tools, and why OpenTofu is emerging as its open-source successor.

What is Terraform?

Terraform is an Infrastructure as Code (IaC) tool created by HashiCorp that enables developers and operations teams to define, provision, and manage infrastructure using code rather than manual configuration.

Instead of logging into AWS or Azure and clicking through dashboards to create servers, networks, or storage, Terraform allows you to describe what you want in simple configuration files written in HCL (HashiCorp Configuration Language).

Terraform then takes those definitions and automatically builds the infrastructure for you.

What makes Terraform especially valuable is that it works across a wide range of platforms, including:

• AWS
• Microsoft Azure
• Google Cloud Platform
• Kubernetes
• On-premises environments
• Multi-cloud architectures

This means Terraform is not tied to a single provider. Teams can use one consistent workflow regardless of where their infrastructure lives.

What is Terraform Used For?

Terraform is used to automate and standardize infrastructure provisioning across nearly every part of the cloud lifecycle.

Some of the most common uses include:

Provisioning Core Infrastructure

Terraform can create and manage foundational resources such as:

• Virtual machines
• Databases
• Storage buckets
• Load balancers
• VPC networks
• IAM permissions

This eliminates repetitive setup tasks and ensures infrastructure is built correctly every time.

Managing Multi-Cloud Deployments

Many organizations today operate in more than one cloud environment. Terraform makes it possible to define infrastructure once and deploy it across multiple providers, helping teams avoid vendor lock-in and maintain consistency.

Automating Infrastructure in CI/CD Pipelines

Terraform is frequently integrated into CI/CD workflows, allowing infrastructure updates to happen automatically when code changes are approved. This brings infrastructure into the same DevOps lifecycle as application development.

Standardizing Environments

Terraform makes it easy to maintain consistent configurations across:

• Development
• Testing
• Staging
• Production

Instead of manually recreating environments, teams can deploy identical infrastructure with a single configuration.

Infrastructure Version Control

Terraform treats infrastructure like software. All changes can be stored in Git, reviewed through pull requests, and rolled back if needed. This improves governance and collaboration.

What is Infrastructure as Code (IaC)?

Before IaC tools existed, infrastructure management was largely manual. Engineers would:

• Click through cloud dashboards
• Run scripts that were difficult to maintain
• Apply changes inconsistently across environments

This approach doesn’t scale well, especially for large teams or complex applications.

Infrastructure as Code solves this by allowing teams to define infrastructure using configuration files that can be:

• Reused
• Automated
• Tested
• Version-controlled
  

Benefits of IaC:

IaC provides several major advantages:

• Repeatability: Environments can be reliably reproduced
• Version control: Code can be tracked, reviewed, and rolled back
• Automation: Infrastructure becomes part of CI/CD pipelines
• Consistency: Reduces human error and configuration drift
• Reduced risk: Fewer errors caused by manual setup
  

How Does Terraform Work?

Terraform operates using two main components that work together to provision and manage infrastructure.

1. Terraform Core

Terraform Core is the main engine. It is responsible for:

• Reading your configuration files
  
• Comparing desired infrastructure with existing infrastructure
  
• Creating an execution plan
  
• Applying changes safely
  
• Managing resource dependencies
  

Terraform Core ensures that infrastructure is created in the correct order and updated predictably.

2. Terraform Plugins

Terraform relies on plugins to interact with cloud platforms and services.

The most important plugin types include:

• Providers: Allow Terraform to communicate with AWS, Azure, Kubernetes, and hundreds of other services
  
• Provisioners: Run scripts or commands during deployment (less commonly used today)

Providers are what make Terraform so flexible and widely supported.

The Terraform Workflow

Terraform follows a simple but powerful workflow:

Step 1: Write

You define infrastructure in .tf files using HCL.

Step 2: Initialize

terraform init

This prepares the working directory and downloads necessary provider plugins.

Step 3: Plan

terraform plan

Terraform shows a preview of what will change before making updates, which improves safety and transparency.

Step 4: Apply

terraform apply

Terraform provisions or updates infrastructure based on the execution plan.

This workflow makes infrastructure orchestration predictable and easy to manage over time.

Key Components of Terraform

Basic Terraform Example

Here’s a simple example of creating an AWS S3 bucket:

provider "aws" {
  region = "us-east-1"
}
resource "aws_s3_bucket" "example" {
  bucket = "my-terraform-demo-bucket"
}

With just a few lines, Terraform can provision cloud resources automatically, showing how infrastructure becomes code-driven rather than manual.

Terraform Use Cases

Terraform is widely used in real-world DevOps environments, which includes the following:

1. Spin Up and Tear Down Environments

Terraform makes it easy to create temporary development or testing environments that match production. This reduces setup time and improves reliability.

2. Multi-Cloud Management

Terraform allows teams to deploy consistent infrastructure across AWS, Azure, and GCP. This is especially useful for organizations with distributed cloud strategies.

3. Complex Applications (N-tier)

Terraform is ideal for multi-tier applications involving:

• Databases
• Application servers
• Networking rules
• Load balancers

Terraform handles dependencies automatically within a single plan.

4. Kubernetes and PaaS Integration

Terraform supports providers for modern tools such as:

• Kubernetes clusters
• Helm deployments
• Datadog monitoring
• Consul networking

This makes Terraform valuable in cloud-native environments.

Terraform Security Best Practices

Because Terraform manages critical infrastructure, security is essential. Best practices include:

• Avoid hardcoding secrets: Use Vault, AWS Secrets Manager, or encrypted remote state
• Secure state storage: Store state in S3, Azure Blob, or Terraform Cloud with versioning and encryption
• Static analysis: Integrate tools like tfsec, Checkov, or Terrascan
• Use Policy as Code: Enforce guardrails with OPA or Sentinel
• Audit everything: Enable logging and peer reviews for all changes

Terraform vs. Other Tools

Tools Comparison Table

Terraform stands out for being:

• Terraform stands out for being:
  
• Cloud-agnostic
• Modular and reusable
• Declarative and scalable
• Supported by a massive ecosystem

Terraform's History and OpenTofu

Terraform launched in 2014 as an open-source project under MPL 2.0. In 2023, HashiCorp changed Terraform’s license to BSL 1.1, restricting certain commercial use.

In response, OpenTofu was born as a community-driven fork of Terraform under the Linux Foundation, maintaining MPL licensing.

Why Use OpenTofu Instead?

• Truly open-source and free to use in any context
• Maintained by a growing, diverse community
• Backed by contributors across the Terraform ecosystem
• Compatible with existing Terraform code and workflows

Why Use Terraform?

Terraform simplifies infrastructure management by turning manual tasks into declarative code. It works across cloud providers, promotes best practices in automation, and scales with your infrastructure needs.

Whether you're launching a side project or managing enterprise-scale cloud deployments, Terraform and increasingly, OpenTofu offer the flexibility, visibility, and power you need.

If you're looking to scale Infrastructure as Code across teams with governance and control, request a demo to see it in action.

FAQ About Terraform and Infrastructure as Code

What is Terraform in simple terms?

Terraform is a tool that lets you build and manage cloud infrastructure using code instead of manually setting it up through dashboards.

Is Terraform only for AWS?

No. Terraform is cloud-agnostic, meaning it supports AWS, Azure, Google Cloud, Kubernetes, and many other providers.

What language does Terraform use?

Terraform uses HCL (HashiCorp Configuration Language), which is designed to be readable and easy to learn.

What is the Terraform state file?

Terraform uses a state file (terraform.tfstate) to track what infrastructure exists and what changes need to be made. Securing this file is critical.

What is the difference between Terraform and OpenTofu?

OpenTofu is a community-driven fork of Terraform created after Terraform’s license changed. OpenTofu remains fully open-source and compatible with Terraform workflows.

When should teams use Terraform?

Terraform is best used when you need repeatable, automated infrastructure provisioning, especially across multiple environments or cloud providers.