Abigail Williams is the seventeen-year-old niece of Reverend Parris. It was a common practice, in Puritan households, for a young woman like her to be employed by a local family, helping out with the household by caring for the children, cleaning, preparing the food, doing the washing, and so on. It was kind of like being a wife and mother in-training.
Seven months prior to the start of the play, Abigail had been working in this capacity for the Proctor family. However, Elizabeth Proctor eventually began to suspect an inappropriate relationship between Abigail and her husband, John, and so she confronted John about it. When John confessed to having an affair with Abigail, Elizabeth fired her.
Since that time, John has recommitted to his marriage and vowed never to break his vows, or one of the Ten Commandments. Though he admits to having some lingering "soft" feelings for Abigail, he says that he will "cut off [his] hand" before he ever touches her again. Though John has moved on, it is clear that Abigail is still very much in love with John. She is bitter toward Elizabeth and says Elizabeth is spreading "lies" about her in the village. Parris, however, wonders why, if Abigail's reputation is so spotless, no one has tried to hire her for their own family since she was let go by the Proctors.