Is `string` a default `type` of a Terraform `variable`?

I can’t find the answer in the docs, hence the question in the title. Are the following variable declarations equivalent?

variable "a" {
  nullable = false
  type     = string
}
variable "b" {
  nullable = false
}

>Solution :

No, it’s stated in the documentation you shared:

If no type constraint is set then a value of any type is accepted.

So basically variable b is set to any type.