What is the difference between doughnut and krapfen? I have been in a shop where you were able to see how they made doughnuts. The first thing I thought was that they were krapfen.

Are there any differences between krapfen, and doughnut? Does one use different ingredients?
There doesn't appear to be any difference. Wikipedia says "In English-speaking countries, Berliners are usually called doughnuts and are usually filled with jam, jelly, custard or whipped cream", and this page says "The English translation of krapfen is cruller or doughnut". There are so many variations of filling, topping, shape and so forth that it is hard to establish a single identity anyhow.