Continental drift is the theory that continents have gradually moved apart over geological time. Initially proposed by Aldrich Wegener, this theory suggests that the continents were once part of a supercontinent called Pangaea, which began to break apart approximately 200 million years ago. The movement of tectonic plates causes changes in the positions of continents, influencing climate, ocean currents, and biodiversity. This concept is foundational for understanding Earth's geological history and plate tectonics.