Espresso machines are as diverse as cars when it comes to makes, models and types. Choose the right machine....
A manual machine is operated by literally moving a lever with your hand. The lever controls a hydraulic piston which creates the pressure necessary to brew the espresso. Very few commercial machines exist anymore operating by this method.
A semi-automatic machine uses a pump to create the pressure instead of a lever. The pour is started by using a knob or switch, then shut off by the user when the pour is done. Attention to detail is required because the barista is controlling the water dosage and therefore the quality of the espresso.
An automatic machine also uses a pump to create pressure, but the volume of water is dosed automatically. This means that the barista starts the pour and the machine stops on it's own when a programmed amount of water has been dispensed. The benefit is that every shot of espresso should be the same regardless of the user.
A super-automatic espresso machine can do it all at the push of a button. Super-automatics have one or two grinders built in. When you select a style of drink, the machine grinds the portion of beans, pours the espresso and some super-automatics steam or froth the milk as well. This means that anyone can make a perfect and consistent espresso or cappuccino every time, with minimal or no training at all.