Amazon Resource Name
From Just Solve the File Format Problem
An Amazon Resource Name (ARN) is a text string used by Amazon Web Services to uniquely identify an object such as a database table, function, or access policy. They are used throughout the AWS services to associate things with one another.
They have the general format
arn:partition:service:region:account-id:resource-type/resource-id, with some of these items being optional, and additional path info sometimes (which can also have wildcards), for instance
AWS uses some other IDs as well, including uniquely generated RequestIDs for each request submitted to a service, as well as "Trace ID" tracing headers. These are generally opaque strings with no obvious semantics.