system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What are some basic concepts of musical theory that will make people better appreciate "good music"?
gpt
Assuming by "good music" you mean western music:

Consonance and dissonance would be a good place to start.  Generally  notes that are very close sounding are dissonant while notes that are well-spaced apart are consonants. 

Dissonant tones will have a beating sound to them which is generally displeasing because the frequency of the pitches.  Play them all the time and people think you don't know how to play at all!  Dissonance creates "tension" that needs to "resolve" to consonance.  These chord resolutions can be inward (two tones move closer to reach consonance) or outward (move further apart) depending on how they are composed.

Start with listening for tension and resolution in music.  Listen to how the composer/author plays with these two conditions.  What emotions do you think the composer is trying to create in you as the song moves through these conditions?