What are the most interesting new features and why do they matter? We've got answers in a Q&A:

How is Apple addressing smartphone addiction?

Well, Apple executives didn't exactly call it "addiction." But senior vice president of software engineering Craig Federighi used a variety of euphemisms for it: "We might not realise just how distracted we've become," he said.

He introduced three iOS 12 features to help limit distraction and help people understand how they're using their iPhone and iPads:

1) An updated "do not disturb" mode lets you snooze notifications and other distractions for a window of time that you choose. And when you use "do not disturb" during bed time, your iPhone shows a mostly black screen until you tap the screen in the morning to dive in. No more midnight peeking!

2) There are new ways to tame the flurry of notifications from apps that want your attention. Pressing on a notification, you can tune how often you'll get them in the future from the app that sent it. Notifications are now grouped by type, app or topic. And iOS 12 will also recommend curtailing notifications from apps you don't often use.

3) The biggest change is a new activity report that lets you see how long you spend using each app, and let you set limits. If you go over your own limit, iOS 12 will pop up a reminder and block the app, though you can grant yourself an extension. Parents can also use this system to monitor and remotely place limits on how their children use their own devices.

What else is new in iOS 12?

Apple said its biggest focus was on reliability and speed, promising apps would load twice as fast in high-performance situations. There was no mention of the impact on battery life.

There's also some new fun to ... get you to spend even more time on your iPhone:

• Users of the iPhone X will be able to make personalised animated emojis, called MeMojis.
• Augmented reality apps using Apple's new AR Kit 2 software let multiple people play games or enjoy experiences simultaneously.
• The Facetime video calling app now supports group conversations.
• New filters and stickers for Messages and FaceTime

What's new with Apple Watch?

It's a walkie-talkie now. Yup, Watch users will be able to send short audio messages to each other with a tap. Each message is preceded by a double beep, so you can live out your movie commando dreams. Watch also got smarter about workouts, and can sense when they start and stop. Watch will also show some simple web pages, such as a restaurant menu or the text of an article, on your wrist.

Also new is the ability to challenge friends to activity competitions, sync and store podcasts from Apple Podcasts on your watch, and add content from third-party apps on the Siri watchface.

What about Mac and Apple TV?

The biggest Mac news at the keynote was that macOS Mojave would bring with it a completely redesigned App Store, which looks a lot like the one seen on iPhones. A new Discover tab has an emphasis on curation, with Apple-produced editorial content shining a light on new and interesting apps. There is now also a system-wide Dark Mode, and an option called Dynamic Desktop that changes your system wallpaper to match the time of day.

Meanwhile, with tvOS 12, Apple TV 4K gets compatibility with Dolby Atmos audio.

When can I get the new software?

Tim Cook said the updates were coming "this fall." That means spring for Australians.  In the past, iOS updates have arrived in September at the same time as new iPhones.

Apple is making beta versions of its software available to developers, but download them at your own risk and certainly don't put them on devices you rely on for daily use.

Washington Post, with Fairfax Media