The Queued Items tab shows all items that have been processed but are waiting in a queue. The queue rules are defined in the Queue tab of a rule. The first column in the Queued Items list displays the rule name that triggered the item to be placed in to a queue.
This list is purely informational. If you need to process a queued item immediately, disable queuing on the corresponding rule and then click the Process button. This will force the applicable items to be released.