From Bushwalk Australia
AKA circuit, loop. A walk that starts and finishes at the same location and where, generally, you do not retrace your steps over the same ground. These walks are not necessarily circular, but can be all sorts of shapes when drawn on a map.
There are some exceptions to not retracing your steps, such as "circuit/loop with a tail" type walks. To illustrate:
1. Draw a circle.
2. Now draw a single line joining the edge of the circle (this is the tail).
In this example you might start at the end of the "tail", complete the main circuit then retrace the tail section to finish.
Some circuits may include "out and back" side trips off the main route, but the central part of the walk remains a circuit.
An advantage of circuits is that you can easily choose to do them in either direction. They also avoid the need to consider transport back to the starting point. This contrasts with some "end to end" walks, which may require arranging transport at each end, such as a car shuffle, where reversing the route is impractical.
A good example of an easy circuit is the Dove Lake track below Cradle Mountain.