Amazon Resource Names (ARN) uniquely identify AWS resources. ARN is required when you need to specify a resource unambiguously across all of AWS such as IAM policies, Amazon Relational Database Service (Amazon RDS),tags and API calls. It is a file naming convention. The format for ARN is given below.
arn:partition:service:region:account-id:resource-id
arn:partition:service:region:account-id:resource-type/resource-id
Arn:partition:service:region:account-id:resource-type:resource-id