In brief, oak brings more complexity to wine. In an unoaked wine fresh fruit flavours dominate, the body is likely to be lighter, tannins will be low and the wine is unlikely to be particularly age-worthy. Most (well-made) oaked wines will have fresh fruits balanced with the flavours from the oak; tannins will give the wine structure but should not be too harsh or mouth-drying and the wine will have a fuller body and smooth mouthfeel.