Planetary transits occur when a planet moves across the face of a star, such as our Sun, as seen from a specific vantage point, like Earth. This event can be observed when a planet passes between the Sun and Earth, causing a temporary dimming of the star's light. Transits are significant for studying exoplanets, as they help astronomers determine the size and orbit of distant worlds. During a transit, the planet's silhouette blocks a portion of the star's light, allowing scientists to gather data about the planet's atmosphere and composition. This method has been instrumental in discovering thousands of exoplanets, enhancing our understanding of the universe and the potential for life beyond Earth.