Continental Drifting is the movement of the Earth's continents relative to each other. An example would be below. Pangea. Pangea is the super-continent that split apart over billions of years. Because of continental drifting and plates splitting apart, the super-continent was no more. So then it created 7 new ones that went different directions.
To prove this theory, a German scientist named Alfred Wegener proposed a hypothesis that said the continents were pieced together and then broke apart over billions of years. He also predicted that fossils that were once on different continents are spread throughout the whole world due to shifting of the continents. To extend further knowledge to this theory, Wegener discovered new evidence that pointed to the seafloors. By mapping, he started to explore the oceanic crust and further extend his curiosity and finally had scientists propose a hypothesis to plate tectonics.