A signal generator usually has various signals that is can generate, such as Sine, Square and triangle. Others have a sweep function and an arbitrary waveform. These are useful tools in the workshop. They can be used to test out audio circuits, op amp circuits and testing circuit response. Most modern function generators can easily put out frequencies up to 1 Mhz.
So, while I did not expect an Arduino based sine wave generator to replace my desktop function generator, I thought it would be interesting to see how to go about designing one and how it would perform.