Question

What are the three types of plate boundaries? How do they form?

Answer 1

here is a good descrption of them (and a cool animation) http://www.learner.org/interactives/dynamicearth/plate.html

but think about it - there are only really three that can happen. Say you have two pieces of cardboard sitting on a table, there are only three ways that you can make them interact. You can push them together, pull them apart or stick one on top of the other (see the link for the proper descriptions :) )