Convergent and Divergent Boundaries. What are they?

Convergent and Divergent boundaries are what neat little things are called that happen when two plates either crash into one another, or separate, respectively. A convergent boundary, when plates crash together, can create hills or mountains. A divergent boundary is when two or more plates separate and can create new land. They can make things called 'rift valleys.' Sometimes they can make mid-oceanic ridges and volcanic islands if done underwater!  There is also a case when plates sub duct under each other.  This causes volcanoes to form!