The document describes three main types of plate boundaries: convergent boundaries, divergent boundaries, and transform boundaries. Convergent boundaries occur when plates collide and include ocean-ocean, ocean-continent, and continent-continent convergence. Divergent boundaries exist when plates move apart, such as at oceanic ridges or in continental rifting. Transform boundaries occur when plates slide past each other horizontally along transform faults. Volcanoes form at ocean-ocean and ocean-continent convergent boundaries, as well as at oceanic divergent boundaries at mid-ocean ridges.