If you're resolved, you're strongly determined. If you've made a resolved decision, it won't be easy to change your mind.
You can also use this adjective to mean "answered," like a resolved equation in math class or a resolved dilemma that's finally been settled. More often, you'll use it to mean "with resolve," or "with purpose." You'll be more intimidated by a debate opponent who has a resolved expression on her face than one who looks uncertain. Resolved comes from the verb resolve, which means "determine," but originally meant "melt or dissolve."