Marriage was a central part of Austen's society and even a financial necessity for most women. As both a moralizer and commentator on society, Austen writes about marriage in Pride and Prejudice to portray common problems and prejudices associated with marriage, especially marriage and class. In addition, she uses the problems and prejudices surrounding marriage to further develop the characters. For example, through Charlotte's marriage to Mr. Collins due to financial need, we learn all about Charlotte's perspective on love and marriage, as well as that a marriage formed out of necessity can certainly be good and beneficial. We also learn through Elizabeth's marriage to Darcy, which integrated social classes, all about her opinion of social prejudices.
Charlotte married Mr. Collins, a man everyone agrees is absolutely ridiculous, simply due to financial necessity. While her father was newly knighted, he quit his business in trade too soon in order to take up the leisurely life of a gentleman, leaving his family with very little fortune to inherit. Since Charlotte has little to no inheritance, she knows she absolutely must marry. Charlotte is also very plain and knows she is limited as to options; therefore, she is perfectly happy to accept Mr. Collins who has an excellent living from Lady Catherine De Bourgh and is also expected to inherit the Longbourn estate. As Charlotte explains to Elizabeth:
I am not romantic, you know. I never was. I ask only a comfortable home; and considering Mr. Collins's character, connections, and situation in life, I am convinced that my chance of happiness with him is as fair as most people can boast on entering the marriage state. (Ch. 22)
In other words, Charlotte is saying that she does not hold romantic ideals of marrying a man she is deeply in love with. Instead, she takes a more practical stance on marriage, knowing that all marriages have their share of problems, and believes that she can be comfortably happy with any man she thinks has a strong character and can provide well for her. Later, Elizabeth observes that Charlotte really is content in her new home with Mr. Collins as her husband. Austen uses Charlotte to show that her philosophy about love and marriage certainly is a practical one and can certainly work. In addition, showing us Charlotte's views on love and marriage serves to show us further insight into Charlotte's character.
In great contrast to Charlotte, Elizabeth marries a man she is deeply in love with, but also one who has equal strength in character and even greater wealth. In fact, Elizabeth faces prejudice from Darcy's aunt, Lady Catherine, simply because Elizabeth has no noble connections while Darcy does. In terms of social status Elizabeth and Darcy are actually equal, as we see Elizabeth point out to Lady Catherine when she asserts, "He is a gentleman; I am a gentleman's daughter; so far we are equal" (Ch. 56). However, Lady Catherine's prejudice against Elizabeth marrying Darcy was a common prejudice among Austen's society. During Austen's era, members of the merchant class were becoming wealthier, and marrying with the landed gentry was becoming more common. Nevertheless, individuals like Lady Catherine persisted on looking down on inter-class marriages and judging them prejudicially. Austen uses Elizabeth's own view of class distinctions to show just how wrongly prejudiced her society really was, thereby providing further insight into Elizabeth's character.