Chapter 2 goes into great detail of the production process. There are three stages of the production process: preproduction, production, and postproduction.
Preproduction, as one would already guess, is the prep stage. The producer is doing everything that needs to get done before the production begins. That all would include preparing for project proposals, scripts, schedules, budgets, research, production management, etc. These are all just formalities so that everything moves accordingly.
Production involves the setup and rehearsal. This is the stage where you have all of your equipment in place, set designs, etc. The director plots every scene and action that needs to take place. The producer handles the audio side of things. During recording sessions and audio production, the producer instructs the engineer, help the musicians rehearse, and just supervise the whole session.
The director deals with the visualization, interpretation, graphics, lighting, casting, blocking, recording, etc. of the production.
Postproduction is the aftermath of the project. From personal experience, I find it very time-consuming. This stage is where you edit the images, sounds, and videos to perfect your production. The editor deals with visual effects, narration, sound effects, integration, distribution, etc.
The reason behind it being so time-consuming is that everything must be balanced out. Great things take time.