A Hair and Makeup Artist (HMU) is responsible for creating and maintaining the appearance of the talent in a video production. They work closely with the director to understand the desired look and feel of the production, and then use that information to style the hair and apply makeup to the talent. A lot of their work is focused on maintaining the look of the talent throughout a production.
For interviews, the HMU will generally do a "no-makeup-makeup" look and keep shine at bay throughout the course of the interview and even during B roll capture.
For narrative-driven projects, the HMU will style the talent based on the creative direction of the project and then maintain that look.