What are ranked matches in Battlefield: Bad Company 2?

In Battlefield: Bad Company 2, their are "ranked" matches, as well as "non-ranked" matches. What's the difference?|||When you play ranked matches, your score is recorded, your rank increases and you get to unlock weapons etc. Unranked get's you nothing.|||Un-ranked doesn't leave a record but is great for training while ranked is where you really go to compete