So I've been trying to understand a few concepts for a while and I'm still confused.

I understand eurorack levels are 10vpp with a /-5V. I also understand line levels (and mic levels? And instrument levels?) are much lower. (What exactly are they?)

And how does a peak to peak voltage translate to something like dBs?

I'm trying to understand how these different levels work, what do mixers and interfaces need to keep clean levels to monitor, mix or record, what do the gain and level sliders/knobs do (attenuation? Signal boosting?). I'm at a point where I want to record some material and also integrate other hardware (guitar pedals, standalone synths like volcas and POs) and all these level/dB differences are being a bit hard to wrap my head around.

Any help/links/resources appreciated!