Gain staging
This is a term that confused me for a long time but a really handy definition is:
Gain staging is the process of making sure the audio is set to an optimal level for the next processor in the chain, in order to minimize noise and distortion.
In the analog world, this is very important: too low of a signal will cause the noise floor to become audible, while too high of a signal will cause distortion. Sometimes distortion is nice – however, this kind of distortion arises from a voltage level exceeding the power supply voltage of a piece of gear which could cause damage. Additionally, even though a small amount of distortion sounds good, doing this at every part of the signal chain could result in a bad sound.