What is the difference between constructive or destructive forces?

(IF you mean constructive and destructive plates boudaries...)
Constructive- Plates moving apart.
Sometimes the earths plates move apart from one another. This is because of the convection currents that force them to move in opposite directions
Magma (from mantle, the thing underneath the earths crust) can escape. This can cause volcanoes. This magma cools and constructs new land like islands we can live on.
Destructive-PLates moving together.
When plates move together they sometimes don't agree.
This happens when an oceanic plate meets a continental plate. The oceanic plate is lighter than the continental plate so has to go under the continental plate. As it goes under it gets destroyed because it is so hot! and because constructive is a volcano making land and destructive destroying the land