The unnamed main character, who is later revealed to be named Celie, writes a first letter to God, saying that she is fourteen, and that she wonders what is happening to her body. She is expecting a child.
Celie writes the first of the novel's 90 letters. A novel written entirely in letters is called an epistolary novel, and it often provides key insights into a character's psyche—insights of which the character herself might not be aware.
Celie reveals that her mother is ill and unwilling, at the moment, to sleep with Celie's father, (referred to here as "Pa," but later revealed to be named Alphonso) because of her illness. Celie's father rapes Celie because of Celie's mother's refusal, and tells Celie she must "shut up" about her abuse (meaning she cannot tell anyone), and must get used to this kind of treatment.
In the beginning, Celie is perplexed by her condition. She knows only that her father hurts her, and that she has gotten "big"—that she is going to have a child. Pa knows that it is of the utmost importance that Celie speak to no one about her abuse, in order to keep his secret. Thus Celie addresses her letters to God, and maintains them as a kind of journal.
After these sexual assaults begin, Celie's father is nicer to her mother, but Celie knows that her mother will not live much longer.
Celie's mother has only a small part in the novel—it is later revealed that she has been mentally ill for some time. It is not clear whether she is aware of Pa's mistreatment of Celie.