For example, the documentation for UIActivityTypeAirDrop
states
When using this service, you can provide NSString, NSAttributedString, UIImage, ALAsset, and NSURL objects as data for the activity items. You may also specify NSURL objects whose contents use the assets-library scheme. You may also provide NSArray or NSDictionary objects that contain the listed data types.
But how do we know what exactly is going to be done with each of the data objects? Do we just need to experiment to find out? Same for the other UIActivity types, none of them say what is specifically done with the objects.