Destructive,Constructive and Conservative Margins

What are the difference between plates made of oceanic and continental crust?

A continental plate is much lighter in density. It is thicker and therefore "floats" higher on the mantle and is above the ocean level. The oceanic plates are denser, less felsic, and are thin and are generally covered by the ocean. Continental plates are generally older. Oceanic plates tend to get subducted beneath other plates. During the process of subduction, lighter material is sometimes forced up with magma that may add substance to the continental plate.

What are the difference between destructive and constructive plate margin?

At a constructive (divergent) plate boundary, new crust is being created to infill the gaps caused by spreading plates. At a destructive (subduction-convergent) plate boundary, old, dense oceanic crust is diving into, and becoming part of the mantle

How is a conservative margin different from those two?

A conservative margin does not create nor destroy. It only moves side by side in the same or opposite direction. Unlike constructive and destructive margins, no volcanic activity occurs here. Although, earthquakes do happen when pressure builds up on the plates.