More technical help...
A disc is turned over when it flies against the natural angle of the disc. For example, an RHBH thrower has turned a disc over if it flies to the right when released flat. This differs from an anhyzer because of the angle of release. Turnover drives are generally released flat or at a slight angle, whereas an anhyzer is released at a more drastic angle. Ideally, the disc will flex back to the natural fade, creating an S curve. Some curves are more drastic then others. A more under stable disc will turn over harder than an over stable disc. Depending on the shot, a certain type of turnover drive may be required. Lighter discs will turnover much easier than heavier discs. An ideal drive for max distance is usually slightly turned over. Depending on the thrower, many discs can be used for turnover drives.