Identify  

Some items have a bit of text associated with them, and you use Identify to find out what it is.

For example, I had a Black Acrylia Halberd, and when I cast Identify on it, I got the message: "Item lore: shadows swirl on the head of this halberd." Or when I cast Identify on a Shield of Shadows: "Item lore: the shield glares at you."

Sometimes it's just fun stuff like that, or sometimes you need to, for example, collect 10 runes all named the same thing. If you use Identify, you would get a different message for each one.