How does the author provide information or details to make the story seem realistic?

While the characters in A Tale of Two Cities are fictional, the background of the book is the real events that preceded and occurred during the French Revolution, which broke out in 1789. Even before introducing his main characters, Dickens describes events of the times in England and France. He writes that the French were "making paper money and spending it" (page 2), which refers to the debt into which Louis XVI plunged the country. Dickens also includes the story of a boy whose hands are cut off and whose body is burned because he did not kneel down to monks passing at a fair distance from him. These types of abuses were real in prerevolutionary France. Later, when describing the poverty of the French countryside, Dickens writes, "All its people were poor, and many of them were sitting at their doors, shredding spare onions and the like for supper" (page 87). They are poor because of the high taxes they must pay, and they suffer as a result. Dickens describes the way people really lived in France at the time.
In addition to including real historical background and events in his novel, Dickens creates characters that, while fictional, represent actual types of people in France. For example, the evil Marquis St. Evremonde represents the avarice of the ruling class in France, and Madame and Monsieur Defarge represent the poor of Paris who watch and wait to get their revenge on the authorities and the aristocracy by storming the Bastille and destroying the property of the aristocracy. Later, during the Reign of Terror, Darnay is arrested and risks losing his life to the guillotine, the real weapon of death that the French authorities used to kill people they deemed enemies of the Revolution, including the French king and queen. Darnay is unfairly targeted for the sins of his ancestors, as were many people during the Reign of Terror.
Dickens creates characters who are based on historical facts, but he also imbues them with fictional flair. For example, while Madame Defarge is depicted based on the experiences of the poor of Paris, she has a particular idiosyncrasy: she records the names of future victims of the Revolution into her knitting. Dickens combines reality and fiction in his novel to create a book that is grounded in real events while offering a distinct cast of characters.