I am not sure what information you already have, so please excuse any repetition.
In the first paragraph of Chapter One of Harper Lee's novel, To Kill a Mockingbird, the reader is given a lot of information about Jem Finch. Jem is thirteen years old, spends a lot of time playing football, and is extremely confident. Despite the fact that one of his arms is shorter than the other, Jem is unbothered as long as the limb is functional.
The second paragraph of the book gives the reader the information that the events in the novel took place several years in the past. Also, it becomes apparent that there is some kind of trouble to come, since the narrator refers to the Ewells as having "started it all." Finally, the reader is introduced to several characters, or at least the idea of them, including the Ewell family, Dill, and Boo Radley. Because these characters are only mentioned, not described in detail, Lee causes the reader to become curious and interested in the events to come.