You are learning about "Change Control Process". In change control the project team is not allowed to make any changes once it has been baselined unless it goes through the change control process. The change control process mandates that a change request can be made but it must go through a change control board to evaluate whether or not the change should be applied to this project are denied for later time within the project.
What impact would a mandated change control process have on the project scope, scope creep and the final project product?