Terraform Language Basics

Basics of Terraform Language

Every Terraform configuration is built from a simple pattern: a block contains arguments, and you reference attributes from resources you’ve created. Understanding these three concepts is the foundation for reading and writing any .tf file.

<block_type> "<parameters>" {
  <arguments>
}

When building infrastructure, the block type tells Terraform what kind of thing you’re defining — resource to create infrastructure, output to expose values, variable to accept inputs.

1. A block is a container that groups related Terraform configuration.

resource "aws_instance" "web" {
  ami           = "ami-123456"
  instance_type = "t3.micro"
}

resource "aws_instance" "web"
   │          │          │
   │          │          └── Local resource name
   │          └───────────── Resource type
   └──────────────────────── Block type

2. An argument assigns a value to a name inside a block.

resource "aws_instance" "web" {
  ami           = "ami-123456"
  instance_type = "t3.micro"
}

ami           = "ami-123456"
instance_type = "t3.micro"

3. In practical Terraform usage, attribute often refers to a piece of data belonging to an object/resource, especially values you can read/reference.

resource "aws_instance" "web" {
  ami           = "ami-123456"
  instance_type = "t3.micro"
}

output "server_ip" {
  value = aws_instance.web.public_ip
}

Here :

aws_instance.web.public_ip
      │        │       │
      │        │       └── Attribute
      │        └────────── Resource name
      └─────────────────── Resource type

Putting them together:

resource "aws_instance" "backend" {
  ami           = "ami-123456"
  instance_type = "t3.micro"

  tags = {
    Name = "backend-server"
  }
}

output "backend_ip" {
  value = aws_instance.backend.public_ip
}

resource "aws_instance" "backend" {      ← BLOCK

    ami = "ami-123456"                   ← ARGUMENT

    instance_type = "t3.micro"           ← ARGUMENT

    tags = {                             ← ARGUMENT
        Name = "backend-server"
    }
}

output "backend_ip" {                    ← BLOCK

    value = aws_instance.backend.public_ip
            │            │        │
            resource     name     attribute
}