Out and back roller coaster
Out and back refers to the layout of a roller coaster. An out and back coaster is one that climbs a lift hill soon after leaving the station, races out to the far end of the track after the initial drop, performs a 180 degree turn and then returns to the station. Some out and back coasters perform more complicated turns at the far end of the track.
This particular design is very popular and is easy to design and construct. With an out and back design the hills on the way "out" usually are quite large and gradually decrease in size. The hills on the way "back" are usually "bunny hops", or small hills created to maximize air-time.
A variation on the theme is to have the track travel from point A to point B, then back to A twice. Examples of this type of ride include the venerable Comet, which was moved from Crystal Beach in Ontario to Great Escape at Queensbury, New York, and the Phoenix at Knoebels' Amusement Resort in Elysburg, Pennsylvania.
These coasters travel back and forth between A and B thrice; the resulting appearance is often hard to discern from true twisters, which are usually free-form in design. An example of this type of ride is the Coney Island Cyclone.
Quadruple out-and-back and higher
While no roller coasters of this type are known, they travel between A and B more than thrice. Like triple out-and-backs, they are hard to discern from twisters, and sometimes wild mice.