To learn additional characteristics of a typical function generator. A function generator provides sine waves, square waves, triangle waves, and pulses at frequencies ranging from a fraction of a Hz to several megahertz. The output amplitude is independent of the frequency. Other waveforms may be provided, and it is often possible to add some DC to the waveform. Better ones also provide a synchronizing ability much like the triggered sweep of oscilloscopes.
Sine waves are easy to generate.
The natural response of an underdamped oscillator in most physical systems, including electronic ones, is a sine wave. Triangle waves are obtained by integrating the square wave with respect to time. Pulse waves are obtained by differentiating the square wave. Many function generators will take the bipolar pulses that come from the differentiator, and use a pair of diodes to provide outputs that have only the positive or only the negative pulses. Also note that the oscilloscope is designed to help you with measurements of rise and fall times.