What are outputs used for?

An output gives a name to a value that callers should see, such as a bucket ARN, a VPC id or a load balancer DNS name. In a child module, outputs are the only supported way to hand values back to the root module.

output "bucket_arn" {
  description = "ARN of the log bucket"
  value       = aws_s3_bucket.logs.arn
}

output "database_password" {
  description = "Initial database password"
  value       = var.db_password
  sensitive   = true
}

Where outputs are useful

• Defining a stable interface for a reusable module
• Printing connection details after apply
• Sharing selected values with another root module via remote state
• Feeding values into automation that reads terraform output -json

Keep output names semantic and stable. If downstream stacks read them through terraform_remote_state, renaming an output is a breaking change. Prefer explicit data sharing through a parameter store or a small module interface when many consumers depend on the same values.