After you have specified your business problem and described it at a high level, you decompose it into granular steps. Then you build the process in the process composer.
An Employee needs to make a business trip and creates an approval request for that. The request contains reason for this trip, place, start and end data, airline company and ticket price, hotel and room price.
The request is then sent to the manager of the employee for approval. If the approver rejects the request, the employee has the option to modify the request and send it again for approval.