In Salesforce, every record has to be owned by a user or a queue. A queue is a group of users who can own records.
From a business perspective, one example is where new leads are placed in a lead queue. Users who are assigned to it can go into the lead queue list view and reassign leads to themselves that they wish to pursue. It can also be the use case where a group of support users is assigned to a case queue. From there these support users can actively go into the case queue list view to reassign cases to themselves. They will then be the owners of any reassigned cases and are responsible for working on these cases.