A queue can have any name, which will be set in the component when configuring a task, p/e a background task could be in an ‘invoices’ queue or just in the ‘background’ queue. Keep in mind that queues do not have priority over each other, so if a task is dependent on something else, plan how to manage timing issues.
Here you can set the queue name for the background process. It will be ‘background’ if left empty.
Workflows, as stated in the example by Stefan, are configured that only one taks can run at a time, to prevent timing issues where something dependant on something else would run before the other task by ensuring they are in the same queue.