If we talk about an espresso maker, there is a variety in the product on the basis of its functioning. Basically there is need to add the same ingredients like water, milk, and coffee powder in each type of the machine. Do you want to know the types of an espresso machine based on the different working procedure?
Pump driven espresso maker: It is said to be a professional espresso maker because in the most of the cafeterias, it is being used. The machine has a pump to make the pressure. This is not preferred for the kitchens at home because it is very expensive. Moreover, it carries high space which is usually not possible in the homes.
Steam espresso maker: It is small in size and good in looking. It is available in various designs and works on pump driven principle.
Piston driven espresso maker: It is a manual type of espresso maker. It is the first and said to be the oldest version of the maker. It is very easy to maintain this type of maker because there are very few parts in this machine.
Stove top or moka pot espresso maker: it is a simplest form of the coffee maker compared to other all types. The functioning of moka pot is almost similar to steam espresso maker. Water is put in the bottom half of a basket attached to the machine and a steam pushes it to the upward side of basket. No doubt, it is less in cost than other types but does not provide the outstanding features also.
Hope so, you have come to know about the basic difference in the features of these machines. If you want to know about an espresso machine in details then you can check this website EspressoMachineInsider that has many details about these machines..