AWS Lambda Permission resource gives an AWS service or account permission to use a function. Not having authentication enabled allows public, unauthenticated access to invoke the lambda function via the function URL. It is considered best practice to require authentication to cloud services.
References:
https://docs.aws.amazon.com/lambda/latest/dg/security-iam.html
In AWS Console -
In Terraform -
References:
https://docs.aws.amazon.com/lambda/latest/dg/security-iam.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lambda_permission