Directors do what they do best, direct people. They send students to their places and begin to start the play. They tell students their lines and explain what they will do, what movements, what accent, guiding the student, directing them.
Orchestra conductors do the same. Most people think that conductors just move their baton to the sound of the song. Incorrect. A baton is moved in a pattern that goes 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4 so that conductors can always direct and tell the performers what beat they're on. So if they get lost they can read their music, see what beat they come into and wait for the conductor to wave the beat.