Extraction
The process of dissolving flavour compounds out of ground coffee into water.
Under-extraction pulls too little and tastes sour and thin; over-extraction pulls too much and tastes bitter and harsh. The aim is a balanced extraction in between.
Extraction is controlled by grind size, time, water temperature and the coffee-to-water ratio working together.
Why it matters for small spaces
Understanding extraction lets you fix a bad cup by changing one variable at a time instead of buying new gear.