"On This Day" app's purpose is...
The source of the information presented by the app is the "On This Day" section of Wikipedia
User can tap any of the "Event", "Birth", or "Death" tabs to view the corresponding data. Selecting an item in the table takes the user to a detail scene where, aside from the initially presented information, reference/s regarding the entry can be found. Tapping on one of the reference opens up its entry in Wikipedia.
Storing the data from the app is doable by using the share button (iOS default implementation) which then links the app to user's other note-taking application.