"학생이 의자를 돌려요."
Translation:The student turns the chair.
So from my pieced together notes (not sure how correct I am but this is what I've gathered from repeating this section):
To Turn (The corner, or like, your body, or whatever object) 돌다
To turn (Rotate/Spin) 돌리다
To return (Come back) 돌아오다
To return (An object to a place/person) 돌려주다
A simpler explanation:-
돌다 is an intransitive verb while 돌리다 is a transitive verb. Transitive verbs have an object, intransitive verbs don't.
So, if someone is turning/spinning something (an object), you use 돌리다. And if something is turning/spinning by itself, you use 돌다.
1. 저는 자동차를 돌려요 - I turn the car.
2. 자동차가 돌아요 - The car turns.