Apple on Tuesday seeded the third beta for iOS 9.3.3 to both developers and public testers. The beta can be installed via the over-the-air update mechanism in iOS, or it can be downloaded from either Apple's dev center or the Beta Software Program website.
The update comes two weeks after the second iOS 9.3.3 beta was released, and it’s mostly bug fixes. Apple is obviously trying to iron out a few remaining bugs in iOS 9.3 so it can turn its attention to iOS 10, which arrived in beta form last week during WWDC.