Neuroeconomics, defined

The application of biology, often using fMRI technology, with economics to understand people's emotions and decisions in economic situations.

There are a number of articles exposing this new field such as:

NYTImes

Psychology Today Blog

http://www.dangoldstein.com/dsn/archives/2005/04/what_is_neuroec.html

But the best way to understand the marriage of neuroscience and economics is to read about the technology's application and usage in other fields. (Which is why we highly recommend Buyology by Martin Lindstrom.)