Hearing judges ratios: each doubling of power sounds like a similar step, whether from whisper to voice or voice to shout. Decibels encode that by measuring level logarithmically, 10 dB per tenfold power change, roughly 6 dB per doubling of amplitude.
Digital audio runs in dBFS, decibels below full scale, where 0 is the ceiling and everything musical lives in negative numbers. A mix might average -14 dBFS with peaks near -1.
The practical rule for reactive design: work in dB, not raw amplitude. A fader, a meter, and an eye all expect equal steps to mean equal-feeling changes, and only the logarithmic scale delivers that.