Ow do the views of constructivist theorists about international security differ from those of neo-realists?

This essay is under the module of security studies for politics degree. As I am an international student I would like the english usage to be normal and not too outstanding. The 2 books listed should help with the essay writing.
Alan Collins, Contemporary Security Studies (Oxford University Press, 2007)
Craig Snyder, Contemporary Security and Strategy (Palgrave 2008), Ch. 2