A rear suspension that allows a wheel to move up and down without affecting the wheel on the other side of the vehicle is said to be an independent rear suspension.
The rear differential of a Subaru is attached to a rear subframe. The various links that hold the wheel carriers to the vehicle also are attached to that subframe.
Instead of an axle across the width of the vehicle moving in response to the wheels' contact with the road, the wheels move vertically, guided throughout their vertical movement by the links. Because they are not attached by an axle, the wheels are independent of one another. One side can bounce down the road while the other remains flat.
Subaru utilizes a double-wishbone link design. The name originally was derived by the shape of the links – that of an animal's wishbone. The two ends of each wishbone attach to the subframe, and the middle attaches to the wheel carrier. Today, wishbone-type links don't always have the shape of a wishbone, but the concept of two attachment points to the frame is still there.