The acronym for LFO is Low Frequency Oscillator, it is an oscillator that generates waves at very low frequencies, infrasonic or less than 20 Hz, imperceptible to the human ear, but very useful for creating unique sounds in your production!
True, this frequency is less than your ears can hear. And to be clear, LFOs don't generate sounds. They make sounds move: in short, LFOs make sounds move, says Dean Friedman.
Why then do you need a signal you can't hear?
They are not used as sound sources: they are signals that are used to modulate other sounds. Then it will be possible to hear an LFO only indirectly, through how it affects other sounds. Therefore, your task is to issue orders to other modules, such as VCA, VCO and VCF.
GO ON AND TRY!
Select a sound or parameter that you want to modify in your DAW.
Go to the LFO section of your instrument or effect.
experimenting with the LFO configuration. You can check how much (intensity or amount) and how fast (speed) the LFO modulation takes place.
Choose the waveform of the LFO (sinusoidal, square, triangular, sawtooth..) to hear different patterns.
LFOs are useful for all kinds of effects, not just synthesizers. Use it and find out how they work best for you. There is no right or wrong when it comes to LFO. No matter how you use them, the LFOs will create movement and the impression that the sound has a life of its own.