I've seen some people ask about this phrase and wanted to quickly shed some light on the subject. Thank you, Wikipedia:
http://en.wikipedia.org/wiki/Guns_versus_butter_model
It's basically the decision made to either spend money on food and infrastructure OR weapons (guns) and defense OR a combination of both. Perhaps this help shed some light on some of FrogBrad's posts.
By way of example, the Civilization series only allows you to have one active project in a city at any given time. So if you're building a soldier, you can't be building a granary at the same time.
