This step will generate html report summaries from your xcresult files. It will also include all of the attachments from your tests.
The step works seamlessly with the official Xcode testing steps. If you use those then you do not need to configure this step in any way because it will automatically discover all of the generated xcresult files.
If you use Fastlane or have script step for your building process then you need to tell this step where to find your xcresult files.