Who is Gretchen aka Margaret from Faust and what is their importance?

Gretchen (Margaret) is Faust's love. She comes from a poor family and is considered a peasant by the townspeople. Faust falls in love with Gretchen immediately, and although, she initially resists Faust's advances, ahe eventually falls in love with him and bears his child. After Faust killed her brother, Gretchen killed their infant child, a crime for which she was convicted and sentenced to death.