An array of instance IDs to be described. If you use this parameter, DescribeInstances returns a description of the specified instances. Otherwise, it returns a description of every instance.
DescribeInstances
A layer ID. If you use this parameter, DescribeInstances returns descriptions of the instances associated with the specified layer.
A stack ID. If you use this parameter, DescribeInstances returns descriptions of the instances associated with the specified stack.