An electronic engineering term. You 'Modulate' a signal in order to impose information onto it.
The empty signal is called the 'carrier' and has no information of itself, it is there in order to carry information somewhere else.
For example a radio wave is an excellent carrier because it can travel through air and space. You 'modulate' the information onto the radio wave and off it goes through the air, ready for you to pick it up. This is how Radio and satellite television works.
The 'information' in this case is a televison or radio program.
It is also how MODEMS work. The only difference being that the wave is not radio but an electronic signal travelling along wires.
In fact 'modem' is a made-up word meaning 'MODulate-DEModulate.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Modulate