# Infrastructure as Code (Terraform Basics)

You've built a server by clicking through a cloud console. It worked. Then three months later someone asks "how exactly is the staging environment set up?" and the real answer is: nobody knows. Somebody clicked some things, once, and the only record is the running machine itself. Rebuild it from scratch and you'll get something *close*, but not the same.

This guide is about getting out of that trap. **Infrastructure as Code (IaC)** means you describe your servers, networks, databases, and DNS in plain-text files - the same kind of files you already commit, review, and diff - and a tool reads those files and makes the cloud match them. We'll use **Terraform**, because it's the tool you're most likely to meet at work, and because once you understand its three ideas, you understand the whole category.

By the end you'll know *why* click-ops doesn't scale, *how* Terraform's core loop works, and *how* to use it without the two or three mistakes that scare people off it.

## How to read this

- **Want it to finally make sense?** Read in order - each phase builds on the last. The whole guide rests on one idea (you declare *desired state*, not steps), and Phase 1 installs it.
- **Already using Terraform and something bit you?** Phase 3 is the safety-and-danger phase: drift, destroy, and secrets in state. Start there.

## The phases

1. **[Why Click-Ops Doesn't Scale](01-why-click-ops-doesnt-scale.md)** - why clicking in a console is unrepeatable, undocumented, and quietly drifts, and the mental shift IaC asks of you: declare *what you want*, not *what to do*.
2. **[How Terraform Works](02-how-terraform-works.md)** - the `.tf` files that describe resources, the core loop `init` → `plan` → `apply`, and **state**, the file where Terraform records what it built. Annotated HCL and real `plan` output.
3. **[Using It Safely](03-using-it-safely.md)** - plan-before-apply as a habit, modules for reuse, and the real dangers: drift, destroy operations, and secrets ending up in state.

> This is the *basics*. Deeper material - writing your own modules, workspaces and environments, CI/CD pipelines that run Terraform, and the testing tools around it - is deliberately left for a follow-up guide so this one stays a clean on-ramp.

**Related guides:** [Cloud Platforms Explained](/guides/cloud-platforms-explained) (what the resources Terraform creates actually *are*) · [Git With Other People](/guides/git-with-other-people) (the review-and-merge habits that make IaC safe on a team).