A dramaturg is a dedicated person on the creative team whose primary task is to support the play's development by asking key questions, starting conversations, researching, providing context, and helping the artists as they work together to tell the intended story.
It is the job of the dramaturg to learn as much as possible about the play (its structure, its language, its themes, etc.) and the context surrounding its creation, then to share that knowledge with the production team whenever and however it is useful.