With the crop selection you can cut out a specific part of the process. This will result in a drill down to all the cases that go through the defined part of the process graph. The resulting graph is previewed underneath the selection input.
In contrast to the process flow, you do not define the exact pattern of the process but only the start and end node that have to be contained in the cases' process. Also cases having additional activities before and after the start and end activity will be included.