what is happening in the historical period/society reflected in the story?

Your question falsl under the umbrella of class structure in the Victorian era, Manners, morality, marriage ....are all heavily dependent upon the rigid class structure of Victorian England.

Class issues are everywhere in Pride and Prejudice. While the novel never posits an egalitarian ideology nor supports the leveling of all social classes, it does criticize an over-emphasis on class, especially in terms of judging a person's character. Ultimately, the novel accepts Elizabeth's view that the trappings of wealth are not a virtue in and of themselves. Darcy's initial pride is based on his extreme class-consciousness, but he eventually comes to accept Elizabeth's perspective, most notably evidenced through his admiration of the Gardiners. Likewise, he joins Elizabeth in rejecting the upper-class characters who are idle, mean-spirited, closed-minded, like Lady Catherine and Bingley's sisters.

Austen clearly finds rigid class boundaries to be occasionally absurd. Mr. Collins's comic formality and obsequious relationship with Lady Catherine form a satire of class consciousness and social formalities. In the end, the novel's verdict on class differences is moderate. Austen seems to accept the existence of class hierarchy, but she also criticizes the way it can poison society. Critic Samuel Kliger notes, "If the conclusion of the novel makes it clear that Elizabeth accepts class relationships as valid, it becomes equally clear that Darcy, through Elizabeth's genius for treating all people with respect for their natural dignity, is reminded that institutions are not an end in themselves but are intended to serve the end of human happiness."