A subduction zone is formed at convergent boundaries by which an oceanic plate slides slowly under a continental plate into the Earth's mantle, as the result of pressure and friction. After a long period of time the overriding continental plate is lifted up creating a mountain range. This is how the Himalayas were formed. Sometimes the extreme heat and pressure exerted on the subducting oceanic plate causes an uplift of magma from the mantle which rises above the surface, creating a volcano. When two plates are moving they don't always slide smoothly. After a while, the plate breaks because of the pressure that builds up. When the plate breaks, the earthquake occurs. During and after the earthquake, the plates start moving, and continue until they get stuck again.
A transform plate movement is where two plates slide horizontally past each other. However, the movement is not smooth due to the friction between the rocks of the two plates. Therefore, sometimes the plates get stuck. With the pressure and tension build up, rocks in the plates break and results in earthquakes.
Mid ocean ridges are places where the Earth's tectonic plates spread apart from each other as hot magma emerges from the mantle and oozes forth as lava to fill the gap constantly created by the plate separation. This is called diverging. As it cools it forms new ocean floor crust. This process is known as sea floor spreading.
When two continental plates move towards each other, they collide. This is called a convergent plate movement. One plate will be forced only slightly under the other from pressure, but no subduction will take place. Therefore, the pressing of the plates will uplift the crust by crumpling and form a mountain. Similarly, when two oceanic plates converge, one may subduct beneath the other. However, there is no straight on collision for two oceanic plates. Magma will then rise up to form volcanoes.