Sources represent either different repositories, such as SharePoint, or they can be different areas in repositories.
For example, we may have a source for SharePoint HR and a source for SharePoint Asset.
We can control which sources are visible for each app.
Here you can see we are only surfacing our ‘Pension Documents’ in the PII and PCI apps.
Its important to note that even if a user has underlying permissions to see the pension documents, they will never see this content via the Search app.
You can see here we are unable to select the ‘Pension Documents’ source in the Search app.