What is the difference between a semi-automatic and fully automatic espresso machine?

A semi-automatic machine gives you manual control over when to start and stop the shot — you grind, tamp, lock in the portafilter, start the pump, and stop it when the shot is done. A fully automatic machine stops the shot automatically after a preset volume. A super-automatic does everything: grinds, tamps, brews, and ejects the puck with minimal user intervention. Semi-automatic machines give the most control and are preferred by enthusiasts.