What are the three main types of plate boundaries and their functions?
Convergent, Divergent, and Transform/Conservative
There are three types of plate boundaries: Convergent, Divergent, and Transform/Conservative.
Since you already know about the concepts of plate tectonics, I assume you already know its basic concept: that the Earth's crust is split into several jigsaw pieces we call as tectonic plates. There are two types of tectonic plates according to density: The lighter Continental/Granitic Plates and the heavier Oceanic/Basaltic Plates. Each plate "floats" on the molten magma beneath the earth's crust, and plate movements are driven by convection currents in the mantle.
Here's what happens on each boundary:
As its name states, this boundary can be found along where two plates collide head-on, leading to the formation of either volcanoes, deep-sea trenches or mountains. Elaborating, convergent boundaries happen when one plate "pushes" to another plate. Good examples include the Western Pacific (with its deep-sea trenches and volcanoes) and the Himalayan Mountain Range (a product of the Indian plate pushing northward to Asia).
Balancing out convergent boundaries, divergent boundaries happen when two plates separate or "split-apart". This phenomena is commonly observed in the ocean floor. When two plates split, magma rises to fill the empty space, and in the process form great ocean valleys and mountain ridges. A good example is the East Pacific Rise or the Mid-Atlantic Ridge.
Transform fault/ Conservative Boundary
In this scenario, two plates neither collide head-on nor separate, but instead slide against each other, like how one rubs their hands together. A famous example of such a boundary is the San Andreas Fault in California. Transform Faults are often epicenters of huge earthquakes.