Definition
What espresso actually is
Pressure, fine grind, short time

A concentrated extraction: ~18g of finely-ground coffee → ~36g of liquid in ~25–32 seconds, at ~9 bar of pressure and ~93°C. The result is syrupy, intense, topped with crema — emulsified oils + CO₂ from fresh beans.
CRAFT NOTE
Espresso is the only brew method where the barista controls every variable in real time. The cup is built, not steeped.