Plate boundaries are the edges where two tectonic plates meet. These boundaries can be classified into three main types: divergent, convergent, and transform. At divergent boundaries, plates move apart, allowing magma to rise and create new crust, often seen at mid-ocean ridges. In contrast, convergent boundaries occur when plates collide, leading to one plate being forced beneath another, a process known as subduction. This can create mountains or trigger volcanic activity. Transform boundaries, on the other hand, involve plates sliding past each other horizontally, which can cause earthquakes along faults like the San Andreas Fault.