A composite resin is a more natural, tooth-like material that can be used to repair a cavity, or to reshape a tooth for cosmetic purposes. It is applied in layers, and hardened to the tooth with a specialized light beam. The bonding helps to protect the tooth from future damage.
Composite fillings are significantly more expensive than silver ones, and may not be covered by conventional dental insurance, because they are categorized under cosmetic dentistry as an aesthetic component. But even if you do have to make up the difference out of pocket, it can be well worth it.