Q.What is the magnitude of Electric Field(E) in the annular region of a charged cylindrical capacitor??

Please give explanations..

And also please specify the meaning of annular region...

Again, you can almost always find answers to these types of questions with a simple Google search.

For example, there's a decent explanation here (http://www.phys.uri.edu/~gerhard/PHY204/tsl105.pdf):
http://www.phys.uri.edu/~gerhard/PHY204/tsl105.pdf

As well as near the bottom of this page (http://dev.physicslab.org/Document.aspx?doctype=3&filename=Electrostatics_CapacitorsParallelPlateCyl indrical.xml):
http://dev.physicslab.org/Document.aspx?doctype=3&filename=Electrostatics_CapacitorsParallelPlateCyl indrical.xml

The annular region is the region between the two concentric cylinders.