What are the differences between an amp head and an amp, and how do they affect the overall sound quality of a guitar setup?

An amp head is the part of an amplifier that contains the controls and power source, while an amp includes both the head and the speaker. The amp head affects the tone and power of the sound, while the amp's speaker affects the overall sound quality and volume. The choice of amp head and speaker can greatly impact the sound quality of a guitar setup, with different combinations producing varying tones and levels of clarity.