Right now, quitting apps on Apple's flagship iPhone consists of swiping up, long-pressing cards in the app-switcher and tapping the minus button. However, iOS 12 will slim down that operation: the extra long-press in the middle is being axed. All you'll need to do now is swipe up once, and swipe up again on the app you wish to terminate. It's a small change, but one that owners of other iPhone models are already familiar with.
During the keynote, Apple SVP Craig Federighi also finally clarified one burning question: will iOS and macOS be merged? The answer was a resounding no, but Federighi did confirm that Apple will allow iOS apps to run on Macs. The company expects to make tools available to developers sometime in 2019.