The difference is similar to "sit" and "set" (and those often confused "lie" and "lay").
You RAISE something else (like a flag on a flagpole) just like you SET something down. It's a transitive verb, which means it needs an object.
But something or someone can RISE by itself. The sun rises, just like the cat sits on the window sill. As in intransitive verb, you don't "rise" somet