Idle & Orphaned Resources
Provisioned infrastructure, such as unattached storage volumes, old snapshots, or unused Elastic IPs, that continues to be billed after the workload it supported has been removed or scaled down.
Definition
Idle & Orphaned Resources are AWS assets that remain provisioned, and billed, after they've stopped serving any active purpose: an EBS volume left behind after its EC2 instance was terminated, a snapshot retained years past its retention need, or an Elastic IP reserved but never attached. None of these show up as an obvious red flag individually, but across a mature AWS environment they accumulate quietly and are one of the most common findings in a cost audit.
In Practice
A development team that terminates test instances but forgets to delete the associated EBS volumes can end up paying for gigabytes of storage attached to nothing, for months, before anyone notices.