What is plate tectonic and describe the rate of motion,seperation and subduction zones ?

Plate tectonics is the study of the movement of the lithosphere that we recognize as plates. Some locations around the Earth come together (conversion zones), where typically, the more dense oceanic plates subduct underneath the less dense continental plates. At other locations around the Earth, the plates are pulling apart from each other (diversion zones). The Mid-Atlantic Ridge would be an example of this type of zone. At still other locations around the Earth, the plates are attempting to slide past one another (transform zones). The famous San Andreas Fault in California is an example of this time of zone. Movement of the plates varies, but it is my understanding that many scientists equate the movements of the plates with the growth of a human fingernail - not very fast for a year. It takes a long time for plates to move what we might recognize as a noticeable distance.