Who is Avril Incandenza from Infinite Jest: A Novel and what is their importance?

Avril Incandenza is the mother of Hal, Mario and Orin Incandenza and the husband of James Incandenza. She is known as the Moms to her sons. She presides over the Enfield Tennis Academy, which was founded by her husband. She frequently has affairs with men, including Charles Tavis, the head of the academy.