How is information transmitted using waves?

In the most extreme case, you can turn the wave on and off completely; this is commonly used in Ethernet for example. You can also modulate some aspect of the wave, such as amplitude (amplitude modulation), frequency (frequency modulation) or phase (phase modulation).Let's consider turning the wave signal on and off. The simplest way to transfer information this way is to agree to send (for example) one bit every second; in that case, if the signal is ON during one second, that might represent a "1", and if the signal is OFF during some other second, that might represent a "0".

In practice, much more than one bit per second is usually transmitted (for example, 100 million bits every second is typical, nowadays, for home Ethernet); and more complicated systems are generally used to encode the signal.