Terraform Concepts

Terraform models infrastructure as code and keeps track of the real-world resources it manages through state.

Core Concepts

• Provider: the plugin that talks to an external API.
• Resource: a managed object such as a VM, network, or bucket.
• Data source: read-only information fetched from a provider.
• Variable: an input value used to parameterize modules and resources.
• Output: a value returned to users or other modules.
• Module: a reusable bundle of Terraform configuration.
• State: the mapping between configuration and real resources.

Why State Matters

• It lets Terraform detect drift.
• It allows plans to compare desired and current state.
• It gives Terraform a consistent view of resources across runs.

Example HCL

variable "region" {
  type    = string
  default = "eu-west-1"
}

provider "aws" {
  region = var.region
}

resource "aws_s3_bucket" "logs" {
  bucket = "my-company-logs"
}

output "bucket_name" {
  value = aws_s3_bucket.logs.bucket
}

Practical Notes

• Keep modules small and focused.
• Use state backends for collaboration.
• Avoid mixing unrelated infrastructure into one root module.