The new unit of the Zerg can attack both air and ground units, She has some fantastic abilities for instance you can enlarge your creep area by putting tumors with Queen on the border of the creep so it will enlarge easily.Also you can increase the larva number by using a Queen ability to the Zerg Hatchery. Queen is strong at the ground but remmeber that she will move slowly outside of the creep so she is designed as a defensive unit while she acts a part in the economy too.