While kicking off its main keynote at the annual Worldwide Developer Conference on Monday, Apple focused on changes to its apps and introduced new software tricks for iPhones and iPads.

It demoed fresh Siri capabilities, for instance, and even a new name for Passbook. And that's just the tip of the iceberg. So, we compiled the most interesting bits below, with the purpose of helping you understand what's different in the new iOS 9 (when compared to last year's iOS 8 update).

Keep checking back for the latest. We'll update as more information comes to light.

What's different or new?

Siri

Apple unveiled a slightly new and more colourful interface for Siri - and it said the personal assistant feature can do way more in the upcoming iOS 9 software update.

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You can say "show me photos from Utah from last August," and Siri will know which photos to serve up and can actually show you them. You can also ask Siri to remind you to grab your coffee off the roof of your car, because the personal assistant can now determine when you're in a car.

Siri is "Proactive" now as well. It can auto-play music when you plug in headphone, for instance, because Siri learns your habits and what you like over time. While demoing new Siri features, Apple also showed us how Calendar can now give you leave reminders based on traffic conditions.

Mail can also look at your email in order to suggest Caller ID details for unknown numbers. Siri can retrieve an invite from Mail and automatically add it to your calendar too, without needing you to open another app. In other words: Siri is getting deeper integration with Apple's own apps.

Spotlight

Apple said Siri and Spotlight have been woven more tightly together in iOS 9, which should enable Siri to suggest things - like contacts - based on your email and calendar whenever you pull down to access the Spotlight panel.

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Apple

Spotlight Search can basically work with Siri to serve up app suggestions, contacts, and way more. You'll also spot videos in your Spotlight search results, which is something that's not available on iOS 8.

And finally, Apple said there is now an API for search: "When a user performs a search, we can find content behind the apps they have on their device, and when they tap they're deep-linked into the app," explained Apple.

Apple Pay and Passbook

Apple Pay will surpass 1 million retail locations that accept it sometime within the next month, Apple said. It'll also come to the UK next month. Other changes include: with Apple Pay in iOS 9, you will also now be able to add store credit cards and rewards cards (in addition to bank debit and credit cards).

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Apple showed off partners like Kohl's, Walgreens, and Dunkin Donuts while on stage at WWDC 2014. The company alsor announced it is working with Pinterest, which is launching Buyable Pins, so you can buy products directly from Pinterest. Buyable Pins are iOS-only for now and coming later this month.

Oh, and Passbook is now called Wallet. Apple didn't say why the name changed.

Notes

Notes now has a toolbar with formatting options. You also get new functionalities with the new Notes app, such as the ability to make checklists, add photos to your notes, draw and sketch inside of Notes, add a link to notes right from the share sheet, and more (and all of this can be done directly from the app).

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Maps

Apple kicked off the segment about Apple Maps by announcing the app now handles more than 5 billion user requests per week (and that's 3.5x higher usage on iOS than the next leading mapping app - likely Google Maps). The company also said Transit directions are finally coming to its Maps app.

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When fetching information for trains, you will be able to tap on a station to see all the lines that run through it (there's even a "multi-modal routing" that lets you switch from trains to buses, etc). Apple said it located all of the entrances and exits to several train and subway stations, such as Columbus Circle in New York City.

Apple also used distance data to calculate your travel time. Transit directions are coming out in select cities first (it will kick off in the US and China). And finally, Apple said location cards in the new Maps app will be able to which merchants support Apple Pay. Pretty cool, right?

News

Apple has showed off a new app for iOS. It's called News and all about "custom layout, rich typography", Apple said.

From what we could see during the demo, News looks as though Newsstand and Flipboard had a love-child. It pulls articles from sources like Wired, The Atlantic, etc, and it updates every time you check it. Every article can feature large photos, graphics, infographics, built-in videos, and interactive elements.

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News also creates a personalised feed called "For You". Other features include the ability to bookmark articles to read it later and an "Explore" feature that helps you discover other news sources or topics you hadn't read before. There's a "Favourites" area for storing stuff within the new app as well.

News will roll out starting in the US, UK, and Australia.

Apple Music

Tim Cook, Apple's CEO, took the stage to introduce something else that's new: "Today we're announcing the Apple Music, the next chapter in music," he said, explaining that Apple Music is a single app that lives on your iPhone.

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Jimmy Iovine, the co-founder of Beats Electronics, a company that was purchased by Apple in 2014, also took the stage to discuss Apple Music and new features to Radio and more. Part of Apple Music is a 24-hour global radio station called Beats One, which Trent Reznor (Nine Inch Nails' frontman) dreamed up. It features DJs broadcasting from three cities.

Neats Music has five tabs/features in all: For You, New, Radio, Connect, and My Music. Beats One streams from within the Radio tab and will be available to listen for free. As for Beats Connect, it lets unsigned artists connect with fans and allows them to upload whatever they want. You can learn more about the feature here.

The new Music app also has a tab called "For You". It shows the personalised playlists and albums you like (and ones picked from a team of experts). There's also a "New" tab that shows new albums and artists, as well as top charts. When using the Apple Music app, you'll see all content displayed in two panes.

The first pane, called the "All", is where the artist's entire library on iTunes is available. The second pane, called the "My Music", can be sound in the menu bar, and it's where locally stored and owned content is displayed. You can also make and share your own curated playlists from this areas.

Siri has been integrated as well, so she can play specific song requests. If any of that interests you, Apple Music will launch with iOS 8.4 and a new version of iTunes for Mac on 30 June. The streaming service will also come to Android this autumn, alongside a new version of iTunes for Windows.

It will cost $9.99 per month, while up to six family members can share an account for $14.99 per month. Apple will also offer the service with a free three-month trial.

Healthkit

Women all across the world will be happy to hear that Apple HealthKit will start tracking “reproductive health,” according to Craig Federighi, Apple’s senior vice president over software, who quickly dropped the tidbit while at WWDC 2015.

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Apple

It was just a brief mention. But the message was loud and clear: with the iOS 9 update, the iPhone's Health app will be able to track a woman's period and ovulation. Finally! Apple announced a bunch of other new HealthKit metrics as well, such as UV exposure and how often you're seated.

iPad-only

Apple showed off a few iOS 9 features that are iPad-only, meaning iPhone users won't see any of these changes (or they already got them in previous updates) First up: the QuickType Keyboard, which adds more tools to the suggestion bar, is coming to iPad. You can also use two fingers on the keyboard to make it a track pad.

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Apple

New multitasking features designed specifically for iPad are also coming. They allow you to work with two apps simultaneously, side-by-side, or in a picture-in-picture mode. The idea is that you can keep watching a video while browsing the web, composing email, or using any other app.

Also, in iOS 8, there was no battery saving mode, but iOS 9 is bringing a a "low power mode", which Apple claimed will provide you with three additional hours of usage. The software update improves general performance too, with Apple emphasising it gives you an extra hour of full usage over devices running iOS 8.

Anything else you need to know?

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Apple

Apple said iOS 9 will work with all the iPhones, iPads, and iPods with iOS 8 installed. It will release this autumn, likely in September, and won't cost a thing. Although the iOS 8 OTA update was a 4.6GB download, the iOS 9 download will be just 1.3GB, which means you shouldn't have to delete anything to get it.