Moral realism is a metaethical view committed to robust objectivity in ethics. No single description is likely to capture all realist views, but a reasonably accurate rule is to understand moral realism as the conjunction of three theses:

The semantic thesis: The primary semantic role of moral predicates (such as "right" and "wrong") is to refer to moral properties (such as rightness and wrongness), so that moral statements (such as "honesty is good" and "slavery is unjust") purport to represent moral facts, and express propositions that are true or false (or approximately true, largely false, and so on).

The alethic thesis: Some moral propositions are in fact true.

The metaphysical thesis: Moral propositions are true when actions and other objects of moral assessment have the relevant moral properties (so that the relevant moral facts obtain), where these facts and properties are robust: their metaphysical status, whatever...