When deleting content items they are per default sent to the recycle bin. Use it to permanently delete or restore items that have been put in the bin.
Use the navigation on the bottom of the list to navigate the items. Select the items you would like to alter and either click "Restore" to restore the items to their original place or click "Delete" to permanently remove the items. Important: Deleting items from the recycle bin can not be undone.
By clicking "Empty the recycle bin" you permanently remove all items.