In English we have two terms to refer to the two types of barrels we can find in the market: “Keg” and “Cask”. Depending on the type of barrel we operate, we need a different pump, in the image below the pumps in the middle are for cask type barrels while side ones operate Keg type barrels.
A keg is a barrel that operates by injecting pressurized gas.
In the other hand Cask type barrels doesn’t have injected gas and therefore it is necessary to exert pressure on the liquid to reach the beer shooter. This type of beer barrels can be found in some British pubs (the only place I’ve seen them) and, unlike the Keg barrel type, they need some kind of lever for the barman to serve the beer by manual injecting air.