Queue ownership and access to queued records
Key Takeaway
The org-wide default decides who can see queued records and who can take ownership of them, and the two can differ. Turning off Grant Access Using Hierarchies for a custom object overrides the queue's own setting, so the object's queued records aren't shared up the hierarchy.
A queue is a shared holding place that can own records, so a team that shares a workload can pick up work from one common list. Records wait in the queue until a person takes ownership. Who can see those records and who can take them depends on queue membership, the role or territory hierarchy, the org-wide default and the user's object permissions.
What a queue is
Every record must be owned by a single user or a queue. Teams that share a workload use queues to prioritize, distribute and assign records.
Queues are available for cases, contact requests, leads, orders, custom objects, service contracts and knowledge article versions. You can also create task queues.