Acid-Base determination of organic compounds
There is a slight error in your sentence. The nitrogen does not have more electrons, but it has a higher electron density because of it's neighbours. But I think this is how you meant it. Often it is described in terms of donating electrons, whilst these electrons are not donated in a cation/anion sense, so I think electron density is a better to grasp description.

Anyway, with being "better electron donors", it is meant that they are more readily able to donate part of their electron density, just like you describe with your description of polarization.

The inductive effect is the ability of an atom or functional group to donate part of it's electron density through $\sigma$-bonds. So in this we are talking about the electronegativity of a group. It is something you have already encountered in chemistry, but this time it has received the proper name 'inductive effect'.

What you would want to be reading, is about Hammett plots. Hammett plots are a tool to picture the ability of substituents on benzoic acid to influence the acidity. Originally Hammett used hydrogen as the reference substituent. The cool thing is that you can compare the effect of substituents on a different molecule, with the effect they have on benzoic acid. I can advise you to get to the library and find 'Modern physical organic chemistry' by Anslyn and Dougherty. Especially chapter 8.2 about Substituent Effects and chapter 8.3 about Hammett Plot's as a tool will be useful.