A symbol is something that has meaning beyond the literal level. A symbol can be a "word, place, character" or, particularly, even an object (Dr. Wheeler, "Literary Terms"). Austen doesn't use symbolism very much, nor figurative language. Her writing style tends to be much more direct and straightforward. However, we do sometimes see some items mentioned that represent larger social issues, or even her own take on a social issue.
One symbol we see in a few places in the book is a reference to reading, particularly novels. Novels were new to Austen's century and becoming increasingly popular as the merchant class began to increase in wealth, allowing more people time and money to be able to afford to purchase books. Since it was the merchant, or middle class, that was clamoring for novels, the novel itself developed a bit of a stigma. Those who read them were considered by the upper class to be uneducated and lowly. Hence, the novel represents the clash in social classes that Austen witnessed in her time, plus many social debates. Austen herself was very fond of the novel. As a result, Austen has characters she thinks are ridiculous, such as Mr. Collins, put down novels, while admirable characters, such as Elizabeth support and openly read them. We hear Mr. Collins put down the novel when he first comes to visit the Bennets. After dinner, Mr. Collins is invited to read out loud, but when he is handed a novel, he starts, begs his pardon, and protests that "he never read[s] novels" (Ch. 14). Elizabeth is seen openly reading a novel at Netherfield when she is staying over to tend to her sick sister. During Elizabeth's first night staying at Netherfield, when she goes downstairs to join the others after her sister has fallen asleep, she declines their invitation to play cards and picks up a book instead. Austen then describes Mr. Hurst, who is trying to distinguish himself from the middle class, as asking Elizabeth in astonishment, "Do you prefer reading to cards? ... that is rather singular" (Ch. 8). Hence, we see that the novel symbolizes a clash in social classes and a large social issue.
Another symbol we see in the book is Netherfield. Netherfield also symbolizes the clash of the middle class and landed gentry. As mentioned above, in Austen's period the merchant, or working class, was becoming increasingly wealthy, creating a new class, the middle class. This middle class was often at odds with the upper class, which consisted of the gentry who had been wealthy for ages. Netherfield represents this social class because, while it is a handsome piece of land, it is actually being rented by Mr. Bingley. Mr. Bingley himself is actually a member of the rising merchant class. His father earned a fortune as a merchant and left it to the next generation to purchase an estate. While Mr. Bingley wants to purchase an estate, for the time being he is actually content not to do so. Therefore, he is content continuing to rent Netherfield and let his offspring purchase the estate, which portrays his current social status despite his new wealth, as we see in the lines:
...but he was now provided with a good house and the liberty of a manor, it was doubtful to many of those who best knew the easiness of his temper, whether he might not spend not spend the remainder of his days at Netherfield. (Ch. 4)
Hence we see that Netherfield is not just a beautiful dwelling place, but also a symbol of the class issues Austen raises throughout her novel.