Welcome to one of my favorite topics: meta-ethics. Rather than describe what meta-ethics is, it might be easier understood by listing some of the questions it tries to answer:
(a) What does it mean for something to be morally “good” or what is it that makes something “good” or “bad”?
(b) What does it mean for something to be morally “right” or what is it that makes something “right” or “wrong”?
(c) Are there objective moral facts or are they subjective?
(d) How can we know if a moral statement is true or false? What constitutes evidence for truth in morality?
(e) Are there objective moral values? What are they? How can we know? What sorts of things count as evidence?
There are 3 major meta-ethical views: (1) Error theory/moral skepticism, (2) Moral Realism, (3) Emotivism/Non-cognitivism. Lets take a (very) quick look at each in turn.
Error theory/Moral Skepticism: This is the idea that (a) there are no objective moral values, however, (b) when people make moral statements (e.g., “doing x is morally right/wrong”) they think they are making statements about what is objectively true. Unfortunately, since there is no real objective moral truth, these people are making errors…hence, error theory.
Most moral skeptics say that moral values are socially constructed and their existence is best explained by considering the culture and ways of life of a particular community. Moral skepticism doesn’t necessarily entail that it’s ok to rape and pillage at will. Moral skeptics can be deeply committed to certain moral values. The key point is only that they don’t believe the moral values are an objective feature/property of the universe.
Moral Realism: Moral realism is the view the (a) there are objective moral values and facts that are a feature of the universe and (b) moral assertions can be objectively true or false and are objective statements about what one should or should not do.
Noncognitivism/Emotivism: Emotivists say that (a) there are no objective moral values or facts in the universe and (b) moral assertions aren’t meant to be assertions about what’s true. Moral assertion can be distilled to emotional expressions of personal assent or dissent for an act. This is sometimes known as the “hooray-boo” theory. When someone says “you shouldn’t lie”, what they really mean is “Lying, Boo!”. Or if someone says “you should help old ladies across the street” they really just mean “helping old ladies across the street, Hooray!”.