In a simple Terraform configuration with only one root module, we create a flat set of resources and use Terraform's expression syntax to describe the relationships between these resources: resource "aws_vpc" "example" { cidr_block = "10.1.0.0/16" } resource "aws_subnet" "example" { vpc_id = aws_vpc.example.id availability_zone = "us-west-2b" cidr_block = cidrsubnet(aws_vpc.example.cidr_block, 4,