I'm no expert in the navigation terminology, but ...

NOAA's Geomagnetism web site Magnetic Calculator Help page ... http://www.ngdc.noaa.gov/geomagmodels/MagneticCalculatorFAQ.jsp?pagetype=0#help8

...defines Declination as "the angle of difference between true North and magnetic North. For instance, if the declination at a certain point were 10° W, then a compass at that location pointing north (magnetic) would actually align 10° W of true North. True North would be 10° E relative to the magnetic North direction given by the compass."

I prefer a compass that has true adjustable declination.

...defines Inclination as "the angle between the magnetic field vector and the horizontal plane (the plane is tangent to the surface of the Earth at that point). The inclination is positive when the magnetic field points downward into the earth and negative when it points upward."

Compasses are sold based upon the global region that they will be used in. Here is a site with a map of those regions:
http://www.wide-screen.com/support/FAQsuunto.shtml#Anchor-60059

Suunto's global needle is specially designed to self-adjust for differences in inclination, so it can be used in any (?) of those regions.