The Plate Tectonics Theory explains that the lithosphere is broken into pieces called plates, these plates move and change size over the underlying mantle.
continental drift is a theory created by Alfred Wegner saying that the continental land masses were once joined together creating a super continent called Pangea. He said that the continents have moved all around the earth creating the land masses we have today. This is different from the Plate Tectonics theory because that theory explains where the plates move and what they are. Plate tectonics is the term used to define the earths crust as divisions, while continental drift is only one of the many processes involved in plate tectonics.
Evidence of Plate Tectonics
paleomagnetism - invisible lines of force pass through Earth and extend from one pole to the other. A compass needle is a small magnet that is free to move about. this needle alligns with the invisible lines of force and points to the magnetic poles. certain rocks and minerals are heated above certain temperatures causing them to lose their magnetic material. however, when these rcks and minerals cool down they become magnetized in the direction parallel to the magnetic field. these rocks posses paleomagnetism.
earthquake patterns - when the depths of earthquake foci and their locations within the trench systems are plotted, a pattern emerges.
ocean drilling - the deep sea drilling project from 1968 to 1983 used the drilling ship Glomar Challenger to drill hundreds of meters into the sediments and underlying crust. when the oldest sediment from each drill site was plotted against its distance from the ridge crest, it was revealed that the age of the sediment increased with increasing distance from the ridge.