Pump or steam?
Several types of machine claim to make espresso-based coffee, but only one really can – the pump type. Pump machines operate at higher pressure than steam machines and employ a thermostat to control the water temperature. The pump both makes the coffee and froths the milk.
Pump machines typically have large, removable water tanks that let you make 10 or more small (demitasse) cups consecutively without having to refill the tank. You can also froth milk for other drinks without making coffee first, as you must with steam machines.