system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Audio files

I know that in video files, the video is broken into frames, which are broken into pixels, which have RGB values. 

What is happening with audio files? What are the numerical values that are actually stored? What do the terms 8/16 bit, 44100 Hz and 128 kbps mean?
gpt
I'll assume you have a vague idea of how analogue audio works - you have some voltage on a wire that constantly changes.  These changes in voltage make your speaker move in & out, causing air to move, creating sound.

When you get into digital sound, you take a *sample* of this voltage and convert it into a number.  This is done thousands of times per second - 4000 Hz (samples per second) is about the lowest that's useable, 8kHz is phone quality, 44.1KHz is CD quality & some high end recording equipment records at 192KHz.  This is your "sample rate".  The other important factor is how much range you have with those numbers ("sample depth") - 8 bit gives you 256 different levels, 16 bit gives you 65536 levels & for high-end studio gear, 24-bits gives you millions.

Hopefully it goes without saying that higher sample rates and sample depths are going to give you sound that more closely resembles the original source.  It's generally considered that 16-bit, 44.1KHz audio is good enough for anyone to listen to (and 24b/192KHz is used in studios when making originals).

That's all for *uncompressed* audio.  When you start compressing audio with lossy compression (like MP3s), you're choosing to *throw away* some of your audio data in order to save space/bandwidth.  In this case, you set a target *bitrate* for how much data you want to save.  128kbps means that you're only using around 128 kilobits of data (16 kilobytes) per second - this used to be considered adequate.  These days, 192kbps or even 256kbps are common.  For reference, uncompressed CD audio is about 1.4 *mega*bits per second.