The Grandfather Paradox is a thought experiment in time travel that raises questions about causality. It suggests that if a person were to travel back in time and accidentally prevent their own grandfather from meeting their grandmother, the time traveler would never be born. This creates a logical contradiction: if the time traveler was never born, how could they have traveled back in time in the first place? This paradox highlights the complexities and potential inconsistencies of time travel, particularly in relation to the concept of changing the past. It challenges our understanding of time, causation, and the nature of reality, making it a popular topic in discussions about time travel and theoretical physics.