Here's why:

* Modulation is the process of changing some characteristic of an electronic signal (like an electric current) to represent information. This "characteristic" could be the amplitude (strength), frequency (rate of change), or phase (timing) of the signal.

Examples:

* Amplitude Modulation (AM) radio: The amplitude of a radio wave is varied to represent the audio signal.

* Frequency Modulation (FM) radio: The frequency of a radio wave is varied to represent the audio signal.

* Digital signals: Binary data (0s and 1s) is represented by changes in voltage levels (electric current) in a digital signal.

Let me know if you'd like more detail on any specific type of modulation!