I love this question. I don't recall it ever being asked before, and settings are under-analyzed in my opinion, considering they make up 1/3 of the main ingredients in any good story (plot, characters, setting.)

Settings are indeed social environments, geographical/physical environments, and historical environments, as you list above. However, a setting can be as vast or focused as you make it.

Say, for instance, your novel takes place in New York City. You might describe the fast-paced people of the bustling city, the high, towering buildings, the constant cacophony of both noise and smell.

However, this is a macro setting. It's a high-level view of the world surrounding this story, and it's not even the highest-level view. You could just as easily consider the USA your setting, and describe the cultural and political influences, the varied geography, and the wide range of people. You could describe "Earth" as your setting, if you protagonist is an alien who happens to be landing in New York City. You might describe the vast oceans and high mountains that make up the earth as you approach the planet.

But you're not just describing a setting to describe a setting. You're writing a novel, and unless you're writing "Cast Away" (please, God, no!), chances are your story takes place in multiple micro-settings. Your New Your City story might, at different times, take place in Times Square, in a night club, in a homeless tent city on Avenue A, and in a stark and bitter apartment converted from an old factory. Each of these micro-settings provides physical limitations for your characters, and the more clearly you see the setting in your head, the better prepared you will be to consider these limitations in your writing. You might also identify several cultural settings on the micro-level. Where the affluent residents of NYC live in comfort and luxury and respect officers of the law for the protection they provide, the poor and homeless might fear the same police officers who, to them, represent a barrier between them and the food keeping them alive.

Your settings list can be very brief to begin, but if you're doing the bonus assignments, you will also create a database of some kind, like you did with your characters, which can be easily updated. You'll describe the "cultural setting" on 10/20, and that can be logged in your database. The settings you choose to describe in detail on 10/6 and 10/23 might be the macro-setting of NYC and the micro-setting of your character's freezing apartment. Or you might choose the night club and the tent city and ignore the macro-view of this setting, because these two micro-settings are more important to the plot. Our worldview changes every time we step through a door or around a corner, so you could literally define a setting in every nook and cranny of your story. How you choose to break apart your settings and define them is up to you, but the exercise of generating a list of settings is designed to force you to think about how you'd like to break up your world, and how the different settings you define affect your characters and plot.

Cheers,
Michelle