The composite resin (white) filling is a ceramic and plastic material that helps dentists fill the cavities or damaged areas of your teeth. Since they look like your real teeth, they can be used in front teeth and they are strong enough to be used in the back teeth as well. They are a bit more expensive than amalgam (grey) fillings and they do not last as long, but they do not contain mercury.
You should check with your dental insurance before getting any type of filling by your dentist, because many insurance companies do not cover the cost of composite resin fillings in the back teeth. Because of this, these fillings are usually only use in front teeth.