[Answered] RMT peripheral: What is meant by a "carrier wave"?

[kolban]

While studying section 7.1 of the ESP32 Technical Reference on the topic of the RMT peripheral, I read the following:

An RMT transmitter does this by reading consecutive duration values for an active and inactive output from the built-in RAM block, optionally modulating it with a carrier wave.

I believe I understand that I can specify the high duration and low duration as a series of record items and supply those to the RMT component and it will produce those on the designated output pin ... but where I am lost is on the concept of a "carrier wave". What does that mean in terms of digital outputs and the ESP32? Does anyone have a description or thought example of how that might work and be used?

[WiFive]

https://www.laser.com/dhouston/ir-rf_fundamentals.html