I've recently discovered unusual spikes in the downloads of my app. I could trace them back to the source type "Institutional Purchase". What does this mean?
Institutional Purchase is indicating the copies of your app bought under Apple's Volume Purchase Program. Any app sold on the App Store automatically become available under the Volume Purchase Program:
All apps on the App Store are automatically available for volume purchase for the same price in Apple Business Manager and Apple School Manager, which is where businesses and educational institutions download apps for volume distribution.
However, if you sell a paid app on the App Store, you can alternatively offer them at a reduced price for educational institutes.