Cognitivists hold that moral statements are descriptive, they attribute real moral properties to people or actions. There are two types of cognitivist: naturalists and non-naturalists.
Naturalists hold that moral properties are natural properties. This means that it is possible to give a complete analysis of morality in non-moral terms, to reduce the moral to the non-moral.
Non-naturalists hold that moral properties are not natural properties, but rather are a unique kind of property that cannot be explained in any other terms. Just as Cartesian dualists hold that there are two fundamentally different kinds of entity in the world, physical and mental, and that neither can be explained in terms of the other, so the ethical non-naturalist holds that there are two fundamentally different kinds of property in the world, non-moral and moral, and that morality cannot be reduced to non-moral terms.