Sway bars are also called anti-sway bars or anti-roll bars.
Their purpose in life is to try to keep the vehicle's body from "rolling" in
a sharp turn. Body roll puts more weight on the outside tires and less weigh
on the inside tires, reducing traction. You want the vehicle to remain
flat through a turn so that the weight stays distributed evenly on all four
tires.
The Teryx comes from the factory with a sway bar in the
rear, but nothing up front.

Kawasaki Teryx
Front Sway Bar

Kawasaki Teryx Rear Sway Bar