Let's say you are a company that makes software for other companies to enable them to make better recruitment decisions. This software can be used as an app or on the cloud. In these circumstances companies often select classes 9 and 42 in their trademark application, and include terms such as "downloadable software in the field of human resources" (class 9) and "non-downloadable software in the field of human resources" (class 42).
These companies often forget (or do not realize it to begin with) that their product/service is not software. It is a a human resources service. Similarly, a banking app is not primarily software, but a banking service. So, always think what service your software is performing and classify it accordingly. For example, banking software is a banking service, not merely software. Software is a technical way of delivering the service to the end user.