Wheel Insets & Offsets - Query

[carboy0]

Hi

I understand the principle of inset and offset, there are several strings here which cover it well. What confuses me is some of the wheel suppliers adverts, they state that a particular set of wheels are 12P or 16P or 12N.

Can anyone explain what these mean. For example does 12P mean 12mm positive (e.g. outset) and does 12N mean 12mm negative (e.g. inset)?

Any advice very welcome, before I spend loads of dosh on the wrong wheels.

Chris