Modulation is the technique of setting parameters to sound generators and sound modifiers statically. Modulation is about _over time_, not about setting statically.
Modulation is an oscillator with a frequency below the human range of hearing. That is a low frequency oscillator.
Modulation is the technique of varying parameters to sound generators and sound modifiers over time. Good job!
Modulation reduces the proportion of the amplitude over a threshold amplitude. That is a compressor.