How do tectonic plate boundaries differ from interior areas away from boundaries-what's found or happens at boundaries, but not usually at interior areas?

Strangely worded question but I think I understand the meaning. So there are three different plate boundary types: convergent, divergent and transform.

Convergent is when plates collide. Specifically an oceanic plate slides underneath a continental plate. As this happens it will produce earthquakes. Additionally, it will produce volcanoes due to something called partial melting which is a little advanced for your scope but basically water gets into the deeper parts of the earth and causes rock to melt at a lower temperature which will then rise up and create a volcano. Because there are two plates with one sliding underneath the other there will be earthquakes and volcanoes and the lithosphere will be thicker in these areas than those in the interior. A much greater abundance of earthquakes and volcanoes in the convergent boundary compared to the interior is also a result.

Transform Boundary's don't really apply much to this question. You will see more earthquakes in these areas but that's about it.

Divergent boundaries are the opposite of convergent and are usually found in the ocean. Plates spread apart instead of collide and magma rises up from the earth to create new land between the plates. This is what creates the "push" the convergent boundaries need to slide against each other. In these areas you will have new mafic and ultramafic rock forming due to volcanism and the rock on the interior will be older and not affected by volcanism unless it lies on a "hot spot".

Hope this helps and let me know if you have any more questions. I do research at NASA on this very topic.