He or she is the one who instructs and guides the actors as to the delivery of their lines of dialogue.

He is also called as the script writer.

He or she builds the set that will simulate the world that play's character are supposed to live in.

Coordinating closely with the set designer. His or her importance is in signaling the entrance of a character, focusing attention on a specific spot-on stage and etc.

He or she studies the general setting (time and place) that the play is meant to take place in as well as each character in the script

He or she should work together with the lighting designer to enhance the mood in the scene or stage.

He coordinates with all the complex behind the scenes details of staging a play.

He not only plans out all the dance steps to suit the music, but also rehearses the actors until they are able to perform skillfully