The Terraform Book

Chapter 3: Building an application stack with Terraform
If you omit the type attribute then Terraform assumes your variable is a string,
unless the default is in the format of another variable type. Here Terraform
would assume the first variable is a string but that the second is a list.
Listing 3.5: Variable type specified
variable "region" {
description = "The AWS region."
default = "us-east-1"
}
variable "region_list" {
description = "AWS availability zones."
default = ["us-east-1a", "us-east-1b"]
}
You can supply an optional description of the variable using the description
attribute.
Listing 3.6: Variable descriptions
variable "region" {
description = "The AWS region."
default = "us-east-1"
}
TIP We recommend you always add variable descriptions. You never know
who’ll be using your code, and it’ll make their (and your) life a lot easier if every
variable has a clear description. Comments are fun too.
Version: v1.1.1 (e771e4d) 6