Excerpt from the Victoria manual:
Population
The foundation of all countries in Victoria is their population. The population is comprised of different types, called POPs, each consisting from 1 to 100000 people and each having their own unique icon. There are ten population types ranging from slaves to aristocrats. Every POP has a religion, nationality and ideology that will affect their behaviour. Two other important variables for a POP are Militancy and Consciousness. Militancy is a measure of how radical the POP is. This is an indication of how willing they are to take action to change society for their betterment. Consciousness is how aware the POP is of its own social situation and how it views society. For example: A labourer with low Consciousness may very well vote for a party that won’t do him any good but “sounds” like the right thing to do since everyone else is voting that way.