The reason some of your items have ?? around them is because they are unidentified. Take the items to a store and click 'Trade', then 'Identify'. The shopkeeper will identify the item for you (sometimes it costs money, though).
Or you can right-click on the item in question and attempt to identify it. Usually you will have a 50-50 shot of correctly identifying it. Sometimes you'll have a 25-75 chance, but that's usually on highlevel items, like the Grim Shields you get from the Barrowgrim Soldiers. If you correctly identify an item, you will get a faint beep. If you flub it, you will get a louder buzzing beep, and won't be able to identify any more items for a certain length of time. Hope this helps!
