The term "about-face" has two main meanings. First, it refers to a physical action in the military where a person turns 180 degrees to face the opposite direction. Second, and more commonly in figurative use, it means a complete or sudden change in attitude, opinion, behavior, or direction. For example, someone might do an "about-face" by reversing their stance on a political issue or decision. The phrase originated from a military command and has since been extended metaphorically to describe major reversals in position or view.
In summary, "about-face" can mean either a literal turn around or a figurative dramatic change in perspective.