ESE stands for "Easy Serving Espresso". The ESE system works on the basis of pods, which are filled with 7 grams of ground coffee. The pods are also called "servings" or "pads". The ESE system was originally developed by the well-known Italian coffee producer illy. By now, the entire coffee industry works according to the standards for ESE coffee and ESE pods. This prevents every coffee producer from developing their own system.
With an ESE coffee machine you can make a tasty espresso at home using an ESE pod. An ESE machine makes coffee in practically the same way as a Senseo coffee machine. The difference is that an ESE coffee machine has a much higher pump pressure. In an ESE machine where you use (for example) illy pods, you can also use pods from other brands. Well-known brands of ESE coffee machines are Francis Francis (by illy), Philips, DeLonghi and Krups.
Unfortunately, ESE pods cannot be used in a Senseo coffee machine. And Senseo coffee pods are not suitable for use in an ESE machine. A Senseo machine does not have enough water pressure to process an ESE pod properly. This water pressure is necessary to make an espresso with a layer of crema.
ESE pods have a diameter of 44 mm, while Senseo coffee pods have a diameter of 70 mm, but both pods weigh the same; 7 grams.