The three main reasons for Four Wheel Steering is to boost your steering response, intensify stability when you're going above the speed limit on the freeway, & even to reduce your turning radius when you're traveling at a low speed. In most vehicles where Four Wheel Steering is included, there is no separate steering wheel; that'd obviously be too much of a hassle. The rear wheels are navigated by a separate computer & actuators. Typically, the rear wheels can't turn as far as front wheels; but can obviously turn the same direction.

When you're traveling at a slow speed, if you turn your wheels to the right, your rear wheels will turn to the left. The reason for this is so it can reduce the turning radius by an estimated 20%. If you are traveling at a high speed, all four of your wheels will turn the same direction because it improves your "lane changing maneuverability" & is more efficient for trucks or vans that usually tow a trailer.