The Plate Tectonics Theory states that the lithosphere is divided up into parts that move over time.
The difference between the Continental Drift and Plate Tectonics theories is that the Continental Drift deals with the continents moving apart, and the Plate Tectonics deals with the lithosphere moving under the Earth's surface.
Evidence for Plate Tectonics:
Paleomagnetism- Certain magnetic rocks are attracted magnetically when cooled after being put under intense heat pressure.
Earthquake Patterns- Earthquake patterns form near trenches, or plate boundaries
Ocean Drilling- A project done in 1968-1983 involved drilling into the ocean floor. They found that older crust was deeper, and younger crust was higher up, therefore proving that ocean-floor spreading is true.
Hot Spots- Scientists were mapping sea floor volcanoes when they found a chain of volcanoes stretching from Hawaii, to Midway Islands, then to the Alueutian trench. They found a hot spot, and discovered that the only way for the chain of volcanoes to form was for their to be plates moving over it, which causes the magma from the hot spot to rise up from in the crust, creating volcanoes.