Signal generators are generally used in schools to generate specific tones or frequencies for use in physics lessons.
Many have a dial where a specific frequency can be selected and some have a LED display which shows the frequency in Hz. (1Hz=one cycle per second) They are usually connected to a loudspeaker so that the specific tone can be heard.
Signal or tone generators can usually be connected to an oscilloscope so that the frequency waveform can be displayed. Some will have enough outputs to connect to an oscilloscope as well as to a loudspeaker. If you only have one output, use stackable plugs to connect to both.
Connection to an oscilloscope is often required in certain physics lessons where teachers can demonstrate how increasing the frequency or volume of the tone affects the wavelength and amplitude of the displayed waveform.
Frequency generators can also be attached to the 'loudspeaker and balls' equipment where the selected frequencies affect the rate at which the balls move (because of the rate of the moving coil of the loudspeaker) They can also be used to generate ultrasonic (frequencies too high for human hearing) and also subsonic (frequencies too low for human hearing) frequencies. They can also be used to generate tones in the 'tin can telephone' practical.