system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: AM vs. FM

What does AM radio and FM radio stand for? What is the difference between the two? Why cant there just be more channels instead of two separate radios?
gpt
You understand writing, like news papers, or the notes mommy leaves dad or mommy’s girlfriend, yes?

And you understand that instead of those symbols we see with our eyes, blind people can read things by touching specific bumps with their fingers, right?

Now pretend instead of symbols like a stop sign, or writing, or bumps, we're using yarn.

Shawn is holding a long line of yarn at one end of the yard, while Gus is holding the other end at the far end of the yard.  Shawn and Gus have worked out two ways to send each other a message with the yarn.

First way: They wave the yarn up and down, and the height of the ripples they make is the thing they look for to change each time to "write" "make a symbol" (like the stop sign) "a bump" (like how blind people read).

Second way:  How many of those ripples that hit Gus, how often and with what spaces in between and so on, are the changes Gus is looking for to tell what Shawn is telling him.

Now, daddy is pretty shitfaced, so try to bear with him.

To understand this idea a little better, think about crayons and music.  While you imagine music, think about all the things you hear.  Not hearing anything is like a white piece of paper.  Hearing so much you can’t tell one sound from another is like a black piece of paper.  Each color of crayon is like a specific sound.  A red crayon on a red piece of construction paper won’t stand out much, will it?  A red crayon on a white piece of paper stands out really well.  This concept is called signal to noise ratio.

Signal is the thing that is supposed to mean something, for example the symbol like the stop sign, the writing, the bumps for blind people, and mommy’s wedding ring.

The noise is the stuff in the background, the stuff that needs to be different from the signal for the signal to make sense.  Noise would be the flat area in contrast to, or “as opposed to” the bumps for the blind folks, or the white background that the black ink of the news paper writes on.

Ratio is an idea that means ‘The amount of a thing compared to another thing.’  In this example, let’s say amount of redness.  Red crayon on red construction paper is a terrible signal to noise ratio.  You’ll have a tough time telling anyone anything with only those two items.  Red crayon on white paper, like the lipstick on daddy’s shirt collar, sends a VERY clear message.  Same for the white stains in mommy’s black undies.  White crayon on red paper tells people your idea better than pink crayon on red paper, which is a little better than red crayon on red paper.

Do you understand a little better now?